You mean to ask me, when did I decided I was a predominantly heterosexual woman trapped in a male body???
Well, it came really natural to me....always was a feminine but didn't feel different from others, however, other kids in school made sure, in not so nice ways, that I knew I was not as masculine as them.
I began to think about men sexually about at 8 years old.....but repressed it greatly, because I felt my mom would kill me. Continued playing with my feminine side, trying to hide it, sometimes successfully, from others. Then when puberty hit, I HATED IT, did not wanted to grow into a man. My gender identification was totally female. That's when I realized I was transsexual... and thank God medicine has being able to help me align my body with my gender (otherwise I probably would not be here).
I have had crushes on maybe two biological girls, but that's rare. My attraction is mostly to men. When it comes to sex, I prefer penises to vaginas, and must be treated as the female as well. :2 cents: