I'm in love with the wrong girl

Ok guys, this is the first time I post a thread here or anywere, the first time I share my love experiences on the internet also.
There's this girl, we were best friends like since middle school, that was most likely 6 or 7 years ago, I never liked her actually, but a year ago we started hanging out again and I met a side of her I've never met before, so as it may come to mind, I fell in love with her, and supposedly she did with me, we started liking each other but she had a boyfriend back then, we keeped contact and eventually she had some issues on her relationship and broke up with him, I obviously didn't make a move cuz it was a little bit too soon to do it so we stayed as friends, back then when we were on middle school we used to kiss a lot and never involve feelings, right now i just get shaky being with her, I now have strong feelings for her but she's always been a very cold girl and never gets seriously attached. I try not to seem very needy and keep my distance even tough on the inside I'd really like to be with her, I've talked to her about my feelings several times and the answer is always the same (I've never asked her to be my gf and i wouldn't)

''I like you too, I'd love a relationship with you and it would work, but not now''

She's a very reserved girl and doesn't hang out a lot, but she's also very pretty and has had lots of boyfriends who got seriously attached to her, I'm not a psycopath nor a stalker but I can't help myself but checking her last hour online or getting really hurt when she doesn't reply back as I am used to. I've never felt this way before and I've never actually cared so much about a girl, I usually am the one who breaks girl's hearts and ignores their messages, when she's not online I can't think other thing but her being with another guy and it tears me apart. I know she is single, I know she's not interested in a relationship right now, I also think that she may have hinted me that I can actually go and kiss her and she'd be okay but also I'm afraid i'd get the cheek by response. To be honest this feeling is killing me, I think I just get jealous about nothing but I can't help myself, the fact that she's not deeply in love with me as other girls might be makes me feel so attracted to her I can't go in a day without thinking what she may be doing.
I don't know if this is wrong, and I don't clearly understand what she feels because she talks to me everyday and she's so cute but also we don't hang out a lot, if I stop replying she'd text me first and get the conversation going, she also gets a little bit jealous sometimes and she tells me but still she shows absolutely no clues that she wants something with me else than friendship.
I'd be okay with that tho, but I'd need time to detach from her and as soon as I stop messaging her she texts me and I usually miss her enough to text her back, we're also best friends so it's kinda hard to just block her and stop talking to her.
She's so perfect to me but she also feels like the wrong girl to love, I'd love to be just her friend and so on but I really have no clue on how to stop thinking about her so much and in general I'm not really sure on what to do about this.
My perfect thing would be her saying that she wants to be with me but I know that's not happening anytime soon.
I wanted to share this because its the first time I have so much good and bad feelings clashing against each other and making me feel real bad sometimes.
I'm also sorry for any grammar mistakes, english is not my first language.

Anyway thanks for reading, I'd appreciate your opinion on this.
Loves y'al Erick 20 y/o

There is a big difference between loving a girl and desperately wanting that girl to love you.

One of these is awesome, the other only causes pain. Get past your desire for her to love you, and then you will probably realise that everything is awesome as it is. Once you are past it, say to her, "I love you, now, stop wasting time, lets get married."

Thanks for the first time share. It's ok to take it slow as friends, but sounds like she's a little confused and don't know what she really wants. Being pretty and having many boyfriends in the past, she enjoys seeing guys run after her. That's why she keeps telling you, " but not now". She bask in the moment. She enjoys being the 'Big catch'. She's playing 'mind games' with you. She enjoys stringing you along. She don't want you, but don't want no other female with you either. (I've had scatter brains like this before, so I know how they think. Trust me on this one).

My suggestion to you (as hard as it my be) is not waste anymore time trying to 'reel' this one in. You're young! There's too many fish in the sea. Cast your line elsewhere.