I know exactly what you mean. I'm sorry it took me so long to respond, I wanted to the first time I saw this post. Pt even said that it's the perfect question for me since I went to a similar situation a few years ago.
Before I started dating pt and while I was single, I had tons of male friends, in fact, most of my friends were guys. I had about four-five close friends that I hung out with on a regular basis. I had no romantic feeling for any of them, they were all like big brothers to me. I loved hanging out with guys, they are far more laid back and easy-going, plus, I liked being one of the guys. That's probably why I am so comfortable around pt's friends and vice versa, since I'm one of the few women that probably gets treated more as "one of the guys" even though I'm one of the guy's girlfriend.
I started losing most of my guy friends when:
1. They told me that they wanted to be more than just friends. Some of them had lame excuses. I remember one telling me he wanted to have sex with me because we were such good friends and he thinks he should show me what good sex was like (because he thinks he's God in bed). Anyways, needless to say, I stopped talking to him.
2. I started having "crushes" on other guys that weren't in my list of male companions. Just random guys I crushed over but didn't develop anything with.
3. And finally I lost the rest of my guy friends (except for the one who introduced pt and I) when I started dating pt.
The thing was, I had talked to all of them about my feelings openly. We talked about how we were only friends, how there's nothing more to it, how I like to hang out with them and that they are like a big brother I never had. They knew of all the other male friends I had and everything was okay until I got serious with one or if I actually was romantically interested in a guy.
Bottom Line: Guys have a hard time being just friends with girls that they enjoy spending time with.
In many ways, we are all the same, I fell for pt because of his great personality, his ability to challenge me, but at first, he charmed me mostly because I loved being around him. We were friend first before we started even considering dating. With you, the guys probably weren't thinking of having you as more than a friend, but you were so cute (as most women can be) and you were so fun to hang out with - they fell for you.
Unfortunately, there's not much you can do about it. Boys will be boys and girls will be girls. Enjoy the time you have with them and if things go a way you don't like or if you get uncomfortable around them, walk away and go find someone new. It applies for opposite sex friendships too, there are many fish in the sea.
You are a charming and fun person, I'm sure guys just are naturally attracting to your personality, falling for you was probably not their plan. You're just that lovable...
Hope this helps....good luck!