Why am i getting these thoughts that im gay when im not? Its ruining my life....

Ok well this weekend has been horrible, I cannot relax and sit down and enjoy things as I usually do, why? Because I'm getting these horrible thoughts that I'm gay when I'm not.

I know I'm not gay ok but every time I think about girls and being with them, like holiding hands with a girl or something (something trivial I think about for most of the day, even at college!) I get this sort of shadow looming over it all, and I don't enjoy it as much, and then some sort ofvile image of things I don't want, I.e gay things.

Im 16, and frankly my first girlfriend was with my best friend who promised me she loved me, and for months (nearly a year) she kept telling me, even when she was having a serious relationship but I wasn't sure because I didn't want to ruin our friendship because I only had one other person like her who lives nearly 3hours away down near london. But eventually after her reasuring me that we'd be amazing together (and I did think we would be) we got together, even though on our date I was still very nervous of losing her, even thos she was my first girlfriend and it had only just started.
For a few days she was SO happy with me, and we planned future things like me going down to stay at hers when she got back off holiday because she didn't want to be alone, and I was so excited. We planned many other things, that were a lot bigger, and she made everything small seem so big, it was great. Day came to our day out (that was her idea even before we were together) and she asked me if I'd kiss her etc, and I said yes of course! And then I went to pick her up and we went to nandos and to see a film, she cuddled me and held my hand for every second we were together it was amzing, and I also paid for it all. Then I made her let me take her home because she was worried about me getting home, because it was 11pm and I was even more worried about her, so I took her home and she invited me in and we had a drink and went into her room, and we talked and had a laugh, then I had to go, by this time it was mid night, and I said bye to her mum and her mum made sure that I'd text her when I got home. So after that my girlfriend saw me out and she walked to the end of her street and then we kissed for well over 10mins under the moon <.< It was so amazing. After that she told me she wished I could go to bed with her, and she said "i don't mean like that, I just want you to snuggle me, you've already made me happier than any other boy" and she kept talking about that. I said I would if I'm allowed, and she didn't think I was so I said my goodbyes and gave her a kiss and walked off. On the way home I felt to proud and happy, and inside I felt complete. Day later she started telling everyone is was so amazing and I was happy she was happy, then later my friend wanted advice and we went on a walk because he was down and then we came back and I had made him happy, but my girlfriend wasn't on msn. 5hours later, she left me.
I think my heart stopped ticking for a second, to only suddnely explode into 200Bpm, and I could think about anything, I couldn't eat, I couldn't do anything. This lasted for 2months, right up until we had a massive argument because I said she ussed me and after that her last boyfriend threatened me, and I had no idea what I had done since she wanted me to talk to her so I was honest. After that we sorted it out and now we're amazing friends again and the other day she said "i love to bits" but I didn't know what she meant, then a day later she hugged me tightly and said it again. I still like her a lot and want her but I have no idea what I'm doing, but back to the subject.
On saturday I was going to work with my dad at 4.30am and I made a joke to my dad "i bet they've come out of the gay bar hahah" and we laughed, but it all ended there.
Since then I've been plauged with thinking I'm gay, and had some thoughts, though I'm not attracted to men, I honestly can't believe it, I'm tearing my hair out, and annoying my close friends about it because I can't honestly believe I'm gay? I've NEVER dreamed of it, but now I just feel that I can't enjoy women as much as normal. By the way I'm 16 and I just heard this is normal but I can't accept it, I am not gay, please help! D:

(Sorry for the wall of text)