Help with girl problems, in high school.?

Ok so I am a Junior and this girl is a Sophomore. We went out two years ago, but we really didn't know what we were doing, we are both shy. The thing is even after we broke it off a few months of dating we stayed friends and I still have a crush on her and don't know what to do. I tried asking her out once again but she just said she didn't want to date in high school. This is killing me. And I don't even know if she actually likes me back. I can't seem to stop thinking about her, even after about two years. And us going to prom together didn't help. On the way home from the dance on the radio a guy said something about him having a crush on someone but the other person not feeling the same, and she said that that must stink. I just smiled and nodded.