I think she's my first love, but there's a catch
Here's my story: I'm 17 years old now. I haven't really had any girlfriends yet cause I'm waiting for that special someone. I'm also what you could call shy, but once I get to know you I'm fine. It's just starting up a conversation with someone that I don't really know I find a little awkward cause I don't really know what to say. I'm the kind of guy that wants to get to know someone really well before I'll even bring up the idea of dating. A little while ago, there was a girl that I like enough to possibly be with but when I finally got brave enough to ask if she would be interested, I found out that she had just gotten together with someone else and they are still together so I just forgot about my feelings I had for her, which wasn't very easy to do, but I did. That was probably a year and a half ago. Now I think I might have found that special someone, but there's a catch, she has a boyfriend already. We have been very good friends since I moved to this school in second grade so I know everything about her. But a few months ago, I started to feel differently about her, and at the time she was single because her current boyfriend had cheated on her. But I just kept putting off telling her how I feel and now she got back together with her old boyfriend that had cheated on her. I mentioned before that I'm waithing for that special someone and that I'm the kind of guy that wants to know someone very well before dating them, and now I know I've found that person. For some reason all of the sudden I just started to feel differently about her. If a day goes by that I don't see her, I'll have to call her just to talk to her cause I miss her so much. Or if I'm in a bad mood at school and even if we just pass by each other in the hall and only say hi, it just makes me so happier. I don't even really know how to explain how I feel about her. I think I love her. I'm also the kind of person that can't stand people who cheat. I've thought about telling her lately but that's what's keeping me from doing it.
Here are the questions that I have:
Do relationships usually last when one of them cheat on the other and then they break up but then get back together?
Am I doing the right thing by not telling her how I feel?
Should I try to move on? And if so what are some things I can do to get her off my mind because I've tried to move on but I just can't.