1 question: Is she using me.. 2 question: Do i have a chance at all?

Well i met this girl in my first year of college. I thought she was kind of cute so i started talking to her.She was kind of shy, which is ok because i kind of like shy girls, but things happened in my life and i didn't pursue the relationship further. Then one year later i found he sitting on a bench crying near one of my schools barking lots. I asked he what was wrong and we had a long talk and , after about 1 hr, she told me the story about how one of here guy friends almost took advantage of her his car. She told me that before that her and this guy were cool with one another and that she thought he was a nice guy. To make a long story short the experience left he traumatized. Keep in mind the fact that i still like her but i could see that at the time she needed a friend not a boyfriend so that was the roll i took on for the next few months. Whenever she cried it was my shoulder she cried whenever she was angry it was me she vented to. Eventually, more or less, she got over the experience but by that time i think is was to late, i think i fell in love with her. I had learned so much about he from all out talks. She wasent just a pretty face anymore.She has such a big heart,she is so kind and loving and smart. She loves to learn, she always want to learn something new, experience something new. I can always find he head caught in some book or online looking up some random fact no one but here would care about. She is one of a kind and i wouldn't change a damn thing about her. But lately i been felling like she been using me. U see she only comes to me when she has problems. Don't get me wrong i don't mind if she talks about her problems to me but that all she talks about to me is her problems. When i see he around school most of the time she wont even say hi to. When i hand out with her friend she acts like i am not ever there. I so many words what i am trying to say is that when shes doing good i dont hear from here AT ALL. I want to tell here how i feel but i feel like it might be too late to pursue a romantic relationship with her. I feel like crap i want this so bad but dont want to mess up the relationship i have. I would want nothing elce in the entire world but to be with he.. but i dont even know if she is using me or not. what should i do? should i go for all or nothing or continue playing the fool.