I'm crazy for this girl!!!!!

Hi I'm new to this forum however I would like go get my this off my chest. Here's my situation. I'm an 18 year old man currently in sixth form/college and I'm absolutely crazy about this girl. She's all I think about day and night and my life has just gotten a whole lot more stressed because of my feelings towards her. I've been friends with her for about a year now and I recently found out she broke up with her boyfriend a few weeks ago. I asked her out a little after I heard she broke up which was about 6 weeks after she did and at first she agreed to a date after expressing some shock that I had feelings for her. I tried to organise a date but she was always busy and eventually she decided she didn't want a boyfriend because she just came out a long term relationship and a few awkward days later we returned to being friends. Since she hadn't rejected me flat out and had not said she didn't like me like that, I thought maybe if I stuck around something could eventually happen between us. She didn't say no, badically just not now. things got a lot worse at a party a little while later where I witnessed two other boys/friends drunkenly fight over her. They weren't just after her for a fling but it seems as though they too are crazy for her. I didn't think much at first since I felt I had a better chance with her than them and as far as I know she rejected them too, telling them the same thing she told me. This drama carried on to the party the following day which happended to be this girls ex BF's. I find out hes still in love with her however isnt a worry to me. I wasn't there but hear one of the boys left with her for an hour and the other ended up crying over her, among potentially 2 fights over her. some said she got off with one of the boys but both of them deny it and say they only talked. it was a mess and I thought the two boys wouldn't be able to come back from it and go back to being friends. Stressed out over this drama and the discovery that I have alot of competition, I go back to college to find her friends with both boys as if nothing had happened, bearing in mind one of them cried over her. this got me thinking she's leading people on. If she isn't interested in any of us she should make that clear. I decide to ignore her for a few days and she ends up confronting me about it so I tell her I think she's leading people on and ask how she feels about me. I don't get anywhere in the conversation she just says she doesn't know blah blah blah. she's naturally, unintentionally flirty even when she had a BF hence why so many boys have a thing for her so in the end went back to normal (more or less). I assume she's not doing what she's doing purposely. Even after my impression of her changed and after she's put me though so much emotionally, I still can't help the fact she's the only girl I want in the world. Im a picky guy when it comes to girls and thus far have never had a GF. I know she thinks I'm physically attractive but don't know what to do. I wish I could just move on but simply can't. when ever I see her spending time in and out of college with the 2 other boys, I hurt inside. Even if she just wants a casual relationship, which I think she does, I want it to be with me. I've decided to change my approach and just spend time with her when I can. I thought since she now knew i had a thing for her it would change things but it didn't really. I don't know what to do. I feel I'm out of options. I'm angry, stressed and sad. I know this is alot of information and may not all make sense, but appreciate any advice/comments.