Any Chance i can get back with this girl?? Please help! Seems no one can??

I Need some advice.=]Ok so it started 3 years ago i used to live in this small seaside town and started working in a internet caf'e. I met this girl there. She would constantly talk to me and look at me, she was in love with me and shizz, i was 17 she was 14. We would spend a lot of time together and every time i went out she would follow , we talked a whole lot and she really was head over heels for me. I tended to be a bit cold and didn't really have the confidence to ask her out. She would say things like talk about the future, and everything and i would to. She would hint to me about asking me if i fancied her when we had a walk, but i was to shy to say anything, i thought she just wanted me to say i did so she could laugh at me (i Know sounds stupid). But anyway, we got on, until a few months later she and her friend were in the cafe i worked at. and they both went on a computer. She sent me a message on bebo saying will you be my boyfriend? (she did like me and other people would also notice and her friends told me) i said yes. We then all left the cafe and walked a few yards down the road. her friend left leaving us to talk.. a bit of silence, she then kissed me on the cheek. i said "Do you want one back". (i know) she then said "it just doesn't feel right. then she walked off home leaving me in the rain.. i stopped and burst into tears,i then went home really depressed. as the weeks went by she acted very cold towards me. I seen a bunch of her friends and her and tried to approach them and she just ran off laughing. She said immature things and what not, lIke i should start cleaning my teeth etc (which i do) ,i was gothy and started self harming worst thing is it was in front of her once. but all she did was laugh at me, she also looked scared, i did it because i was angry at myself and wanted her to feel sorry for me and like me again.. Anyways i ended up moving due to family however still have her on facebook msn etc. a year passed and she messaged me on MSN (About six months ago) we were talking and she was being nice and asking me how i was,also told me not to do anything silly again i told her (i done a lot of growing up and wont ever do it again) , anyway we chatted for ages and she told me about her boyfriend (which she has now been with for a year) (shes 16 now). and was sorta slagging him off a bit like how he can talk to other girls but she cant to boys. He was on holiday and would phone her everyday, she even told me she sniffed his jumper he left because it had his scent. i told her about my nan who was ill and she said "We been friends for a long time now so i will always be there for you" she also said stuff like she couldn't ask for a better friend. Six months later (present) (no messages off her) i went down there on a trip for a few days (its a small town) i managed to bump into her and started talking, she seemed pretty uncomfortable. Probs because its a gossip town and if her friends seen me and her together it might stir a fuzz with the boyfriend. But i was nervous to i would question her (she was on her way home and i started walking in line with her) asking how different things are and she would give small answers,she laughed a little and would smile quickly. I said i had to go a different way back to my hotel. Then i Said "Keep in touch Yeah"? She Said What? I Repeated Keep in touch ye? she said yeah and looked a little nervous. we then departed. i am back home now (100 miles back) and she doesn't realize just how much i love her, i just was scared but im confident now, But i don't know how to talk to her, Seriously shes the only girl on my mind ( I Have this problem of keeping feelings to myself). I Know i sound like a Pig but i really do like her and want to ask her out and tell her everything i felt and still do . but i was scared because of her age, because, of my feelings. I Just don't know what to do shes 100+ miles away and i acted like a idiot, but i know she still likes me. i even still got a piece of tissue she wrote her name and a autograph on.to me (like a love note) which i was thinking of showing her one day. I Know i acted like a idiot,i know i shouldn't have done that and i know she could probably do better. But please help me talk to her , im scared of her ignoring me if i message her on facebook,What should i do? do i tell her everything? or wait for her to finish with her boyfriend? I Know i sound selfish but i don't want to date anyone else only her and i never opened up to her. What can i say?