Teenage sexuality help? Please?

Ok, so here is the story. I just turned 16, and I feel like breaking down over this whole situation. It makes me upset to really think about it and the one thing I could think of was coming and asking for help or advice. See, a year ago or so I was curious as to what gay sex was, looked like, whatever. It seemed like the fact I thought it was prohibited made me wonder about it more, so I looked up gay videos on the internet. All my life though, I have fallen in and out of teen love with girls, and never really looked at a guy and wanted him. I mean sure, I can say a guy is good looking, but I've never really seen a guy and wanted to have sex with him. Throughout my days recently, I will think I am straight and positive of it for a little while, then my worries come back at the thought of being gay, and I immediately try to get it out of my mind. I can't tell if this is just a phase, hormones, or what, but it is making me sick. Does this happen to alot of teenagers? When does it stop? How can I put an end to it?