This is something a lot of people wonder about when they're in their teens. Point is, if you are, it's not the end of the world. On the contrary. This is also not a decision anyone else can make for you. But nothing is more stressful than trying to be something you're not, so make peace with what you are, whatever that may be, and get on with your life.
Get as much information as possible. Read the sexologist's article titled Straight, gay, or bi?.
If it does turn out that you are gay, here's some advice on telling your parents.