Can't figure out if I'm bi or straight...?

Ok, I'm 15 years old and I've always sort of had this nagging suspicion that I might not be entirely straight, but then again that might just have been me worrying about something just for the sake of worrying, as I'm a chronic worrier. Anyways, it would be these weird feelings that sort of felt like I was jealous of other guys, but it was also this weird thing where I wanted to become really good friends with them, to sort of make me matter in their life. And this went on for a while with different guys, but then recently that sort of went away, and I made new friends in high school that I became a lot closer to. Now when I get in a situation where its just me and them, I get this weird feeling in my stomach, almost like butterflies. I sort of wonder what it would be like to be with them, but then if i actually think about it in detail I get grossed out. I tried watching gay porn, but it didn't turn me on at all, but I'm definitely turned on by the straight stuff, and I made out with a few girls at a party and it definitely turned me in and was a lot of fun. Am I crazy about possibly being bi, or am I just going crazy?

Thanks and no nasty comments please.