PLEASE HELP? I have a complicated love story and feel so lost

Hey there, so it's a long story so here we go. My first semester in university I meet this amazing girl in acting class. I was 17 almost turning 18 and she was 22 and in her last semester of university (funny timing). She's every bit like me, she's super outgoing, loves to joke around and is nice to everyone, she's one of those "I'll trust and be kind to you until you do something to make me think otherwise" girls. We gradually became friends through hanging out with the class alot, and we started to text each other alot and I'd joke (partially) flirt with her because she already had a boyfriend of 3 and a half years. I'd always joke flirt with her saying "Your really beautiful, it'd be a shame if I could never kiss you" and other cute stuff like that and she'd like the attention. So we became closer and closer, cut to the chase it's 1/3 into the semester and I invited everyone in class over to my house to study for the midterm. Surprisingly due to pure coincidence everyone except for her cancelled at the last minute all with different reasons. So instead of studying because we couldn't concentrate with just the two of us, we watched the movie Up, I joked around again and got her to lay down next to me and cuddled with her during the movie (she has a boyfriend, don't forget). And I started to develop feelings for her right there, and I'd convince her to let me kiss her with the excuse that my birthday is coming up and that it'd be the perfect gift for me. Anyhow, she turned around and kept faced me on the bed and kept denying me but gave me strong signals to do it anyways. I leaned in and she didn't back up, I kissed her and it was amazing. After she said "there, only because your birthdays coming up and that's my early present to you". For the rest of the day we cuddled in bed and I'd try to steal as many pecks as I could. Eventually she left for home and at this point I was texting her all day every day.

I asked her over text if I could kiss her again, and we had a little back and forth but eventually she let me. Then over the next week or so we'd give each other cute kisses when no one was around and she asked "Do you ever wonder why I'm doing this with you? When I already have a boyfriend?" I asked why and she replied "Because I know your not serious about us and we have no future together, so I don't really care hahaha". I laughed along as well but I knew deep down that wasn't the reason, and it wasn't. Over the next few days she became more hesitant about kissing me because she started to feel guilt and didn't want to betray her boyfriend, but however many days passed and we still haven't stopped. So eventually it was my birthday, I asked her to spend the day with me and she agreed, so she came over and brought me a gift (a very expensive iPhone case) and we spent the day cuddling in bed, watching movies and kissing again. When night came, we went downtown with other friends for a big birthday dinner.

Eventually me and her grew closer and closer not only with feelings for each other but also as best friends and it was the greatest thing in the world. I haven't felt this about someone for a long time. We texted every minute of every day until 3am and we'd wake each other up with texts in the morning, and when we weren't texting we'd see each other all the time either grabbing lunch before class or hanging out after or during class. Basically for an 4 months she was in my life every single day. After some time the teacher announced that we we're going to be partners for our final acting performance playing a sex scene. We got to spend even more time together seeing as we would rehearse (just an excuse for us to hang out more) outside of class and rehearse during class as well. It became so comfortable that both me and her forget that she had a boyfriend almost for a minute. I slowly wanted more and more of her, originally she said "only kissing, thats it, no tongue, no touching, nothing else. otherwise i'll feel like im cheating on my boyfriend". But eventually as time passed she'd come over 3-4 times a week, and we'd lay in bed, put on a movie and kiss, then it turned into making out, then it turned into groping, then it turned into us taking each others clothes off and then before you know it, we had sex. But by this point I fell so hard for her and she for me (although she didn't admit until later, aka keep reading) that in some un-explainable way, it felt right.

From an outsiders POV everything about what we were doing was absolutely wrong but between us it was so right. We both couldn't explain why we were doing what we were doing but we didn't want to stop. We fell for each other as best friends and lovers. So now we'd spend almost every minute of everyday together and I'd hold her close when we walked, I'd kiss her whenever I can and she'd come over all the time and we'd make love and just cuddle in bed holding each other. Earlier on she has confessed to me that she doesn't love her boyfriend as much as she used to anymore, and that after 3 1/2 years she doesn't feel the love progressing any further. It didn't matter to me, I was so bliss in the moment of me and her that I couldn't think of anything else. One day as we were about to have sex she stops me and asks "we do this every time.. sometimes I wonder if I'm anything more", but I know this wasn't what was bothering her. I knew her so well I could read her like a book. She knows I love her more as a best friend and I'd go out of my way to do anything for her. The real problem was that she was now feeling so guilty for cheating on her boyfriend that the guilt was eating her alive and she couldn't bear sleeping with me everyday and going home to him and falling asleep in his arms. She asked me if it was okay that we stopped doing everything and just stayed best friends and bro/sis. Oddly enough I cared for her so much that if that's what made her happy, despite my misery I would support her no matter what. After all we promised each other from the beginning that no matter what happens, we'd always stay best friends and never leave each other side and always hang out and keep this friendship alive even after shes done with school.

The night of this, she was hesitant on her IMs and I asked her what was wrong to which she replied "I dont know, I'm so confused, I don't know what I want anymore." and to make a long conversation short, she basically subconsciously said "I don't wanna just be friends, I want back what we had" but without actually saying it. So the next day she invited herself over for a "study session" for the final exam. We basically talked it out and she said she didn't want me to give her up, she just didn't want to lead me on. I assured her there was no issue. I leaned in to kiss her as a test and she pulled me in, as I was taking her clothes off I said "I'm sorry, I'm sorry I promised you I was going to stop this" and she said "It's okay, I want to". So now in a matter of 2 months, a girl who first said "Theres not a chance in hell between us, I have a boyfriend and your not even close to as great as he is" is now falling for me and wanting me. Soon school had ended, everyone's lives moved on and drifted apart except for us. Me and her texted every minute of every day as usual and went out of our ways to make time for each other. I'd still take her to movies and dinner and she'd come over and we'd still make love and cuddle. Life was great.

Until one day she phoned me and said "I just broke up with my boyfriend." The news hit me like a shocker. It's technically what I've always wanted but it felt so unnatural. They've been going out for 4 years. I knew she liked me but no way enough to leave him for me. She assured me it had nothing to do with me and that they've been having relationship problems and that it was going to happen regardless of if I was in her life or not. But the second she broke up with him she regretted it and wanted him back, because for the last 4 years she's depended on him for everything and now that he's suddenly gone, it was too much for her to take all at once. Her parents and family were all gone in Hong Kong, she was living with him because she hates being alone, it was 2 days before Christmas. She was actually alone with NO family and no one on Christmas Eve for the very first time in her life. She moved her things back home and I stayed on the phone with her until dawn just listening to her sleep, making sure she was okay. The next say she saw me and the tears were even worse. Her and her boyfriend are huge basketball fans and have been planning a trip to see the Lakers in January in LA for a year now. When her boyfriend sent her a text about ticket cancellations she freaked out even more. That night she decided to go see him and give them a second chance, they came to the conclusion to go on a 3 week break until their trip to LA, take the trip and decide after if they're meant to be together or not (the boyfriend has no idea about me at this point yet). So for the next week I stayed on the phone with her every single night from when she got off work or hanging out with friends until roughly 7am, and we'd just talk and I'd keep her company.

Slowly things started to change between me and her, she didn't want to kiss me anymore. Her lust for me drifted away and when I asked her why, she said "Seriously? Not with all this that I'm going through right now". Eventually when I met up with her to give her her christmas gift I asked "Would you feel better if we just stopped doing all this and just became friends?" and she said "Yes". So despite all my pains, I swallowed it down because I knew she just needed me as a friend more than anything right now. So roughly a week and half since her and her boyfriends break-up passed. One night me and her were talking on the phone and she sensed that I sounded a little off, eventually she fished it out of me, basically I said that she broke almost every promise she made to me, I've kept every promise I've made to her and that despite losing her I would still be there for her as a friend because I genuinely cared about her happiness and I had no bad intentions to begin with. She cried and said "I never doubted you once, your the best person I knew, I'm not worth it, seriously". I stuck by her side nonetheless and I know she was so grateful for it. One night she called and said "I'm going to tell my boyfriend everything, the guilt is killing me, I can't sleep or concentrate, I need to tell him". As always I supported her decisions no matter what. So she told him everything thats been happening between us, and they yelled and fought all night, basically the end result was that he still wanted to take the break, go on the LA trip with her and then decide if he can ever trust her again and have a future with her. She called me the next morning and said "I'm going to keep it short, basically if I might have a second chance with him, and if there's even the slightest chance that me and him could have a real future together, you (me) can't be in the picture." I said "What do you mean" she said "You can't be in my life, we can't be friends anymore, we can't know each other" and she tried to keep a collected neutral tone as she was saying this. I said "So thats it, after you broke promise after promise. You break the last and most important one there is, that we'd stay friends no matter what". She broke down crying and said "I'm so sorry". I said will I ever hear your voice again and she said she didn't know. We said our final goodbye on the phone.

Afterwards I felt at such a loss for words. What could I say? This was the FIRST girl I've ever fully trusted and let into my life, she knew me like an open book. There were no secrets I hid from her. I gave her everything and from the start had not even the slightest bit of ill intentions. It's been two weeks now since, I've thrown away every memory of her, everything she ever gave me and deleted every picture, basically removed every trace of her from existence. The only way I even know that she exists in this world is through the mutual friends we have and my memories which I can never get rid of. These two weeks have been the longest and toughest of my entire life. Not a moment goes by when I don't think about her, she pops into my mind with everything that I do. And it kills me so much right now that she's in LA as I type this with her boyfriend, and I'm sitting here in my room. More lost than ever in my entire life, and more miserable than before this all began.

Bottom line. What do I do? Please give me thoughtful answers and suggestions, there's no dumb answers. Please help me. And please don't scold me about how what I did was so wrong and blah blah blah. Please just help me through this. I'm young and inexperienced and could really use some advice. I'm trying so hard to let go and move on but it's just not working or getting any better. Help

*If the story wasn't fully detailed, please feel free to ask about anything and I'll be more than happy to answer