Believe it or not I know exactly what your going through because when I was 16 I was so convinced I was straight I Wen't through 2 boyfriends in 12 months anyway.
After the second one broke up with me I almost fell into tears every other hour then one day I got a message from him on my mom's awnsering machine telling me to go meet him for Coffee at the local Tim's and when he was there he bought me a Chamomile Tea and asked what I thought of his Fraternal Twin sister, I replied with She's good looking and would probably make a man really happy one day.
He asked me to go over to his house for awhile of course I accepted when we got there his sister had asked me to talk with her for a little bit and we did and then she asked me what I thought her body was I replied with its Hot and will no doubt make a man fall to his knees then she wispered in my ear that she wouldve rather pleased me with it and then kissed me on the lips I was stunned but it felt Natural it was like a force I had never felt before.
As the months wen't on me and her grew closer and closer till eventually she moved to NeW York she writes to me and tells me sweet stuff on the phone I still love her.
Anyway my experience kind of doesn't end up like yours but its always good to see sopmeone you can sorta relate to in uncomfortable places of mind like that.