I was "only into women" before I transitioned, but that's kind of a lie. I was in a situation where I couldn't really explore that stuff. I messed around with guys a couple of times, but was intensely uncomfortable being made to feel like a girl. I stuck to dating women because it was easier to feel like was in the male role, or something like that.
However, I can't deny I was often attracted to men in those days. During one drunken experience I told this boy, "honey, you're as pretty as ANY GIRL..." lol lol lol.
Now that I'm presenting as male, although I'm still pre-t, I feel WAY more comfortable with my sexuality, because I can think of it as a guys sexuality. One week, I'll be all about the dudes and fantasise about gay sex endlessly. Then suddenly, I'll be like, hey I miss boobs, and start thinking about girls. I'm really interested to see what happens post T.