Why does seeing her with another guy hurts so, so much? Help...

I hope you can take your time and read this, I really need help.

I fell truly in love for the first time in my life with this girl who used to go to the University with me, we were classmates and soon after we met we became close friends. I'm not gonna talk much about it because I really went through alot of pain with her, but the point is she pretty much made me think she had a crush on me and whenever I tried to start something she would back off or she would just simply say she didn't thought of me as a boyfriend or anything like that. It was pretty much 8 months of that crap, me feeling really bad hoping one day she would realize how much I cared for her and how much fun we had together so we could finally be together. Often she would make me feel bad on purpose and I underwent some really, really tough depressions. She, on more than one occation, made me think she was with someone else. Eventually I told her I had enough and told her we weren't gonna be friends again. Next day, she comes to the classroom with a bouque of flowers. I was heart-broken, devastated to say the least. But I kept my cool. A week passes and she texted me, said she wanted to talk. Next thing you know, bam, we're "friends with beneficts". We lasted like that for a month but I was really jealous, and we always said to each ohter that we cared and stuff. We were pretty much boyfriend/girlfriend but she didn't want to admit it.

So, she got tired of my jealousy and left me. By that time, my grandma had just been diagnosed with cancer and I was really sad about it, it really got to me. I texted her a week after she left me saying that if she really meant those "I care alot for you"s and those kisses and time we spent together, that it was time that she told me because I really needed her in my life. She said she was sorry about what happened to my grandma but said she didn't care for me. Tried talking to her the next to weeks but nope, we just had fights till eventually she said I was fake and told me to stop calling. And so I did. I moved on with my life. A month later... Bam, she texts me, looking for a shoulder to cry on, for a friend, the same friend she refused to be to me month and a half ago. I helped her, comforted her, and eventually we got together again. She was very manipulative and every time we had a little argument it would end up on her saying the relationship was over. That happened 7 times in one month until she just didn't answer back. I tried texting her for 2 weeks until I gave up. A week later, she texts me, on Christmas Eve, saying she had something mine that she wanted me to have, some stuff we ordered online I assumed.

She drops off by my house on December 24, doesn't even get out of the car, just rolls down the window, gives me what we ordered online, and a bag with some clothes she borrowed from me. I tried to stop her from leaving, I told her that I knew she cared and that I loved her so much, I placed my hand on the back off her car seat and she rolled the window up to crush it. I, in tears, told her that I made a promise to her never to let go, because I knew the tough crap she had gone through in life and that she deserved someone that cared. She just told me to back off, and drove away. Guys, at the bottom of the bag, there was this gift I gave her when we were starting to date, when I told her I really cared for her. That, in particular, really made me feel bad. I was there for her all the time, and she had left me again - in tears - after all that I did for her.

Each month that passed, I tried talking to her, and she blocked me from Whatsapp everytime I did, claiming she didn't feel anything for me. And each month that passed, she unblocked me again, just for the process to repeat itself. 5 months ago, I told her I had enough and pretty much said everything I wanted to say for a while. Told her it was easy living on your own when your family pays for all your expenses, when you get a free car and a job you can go to whenever you feel like it. Told her that she wasn't pretty at all, called her average at best and told her that without her fake tits she wasn't anything, that she was all about surgeries. That's hwne her manipulative attitude ended, I didn't talk to her again since then, not I stalked her on Twitter, FB, anything.

I thought about her alot because she was my first love, but yesterday I found out she was dating someone else, and that really made me feel like crap. I thought I was over this, I even started dating someone else myself 3 weeks ago, but dammit, it hurt alot. As soon as I got home I vomitted and cried like a 5 year old. It pissed me off seeing her smile with that guy. This girl did alot of damage to me and all of my friends adviced me to leave her when we were together and I didn't listen to them. I can't keep thinking about her, she doesn't deserve it. What can I do to forget her once and for all?!

Thanks in advance, I understand this is long.

Remove her from your life and do not ever talk to her again.

She is a user and just using you.

That's what my best friend told me man... I fell for her like a fool, thankfully I managed to keep her away with the awful things I said to her, I know it's for the best but it still hurt seeing her with another guy. Thanks for your reply :)