Well, my first fantasies (around 13 y.o.) involved men. But I was always a female there... I could never engage into anything sexual with guys while my body was reflecting theirs (at least, mostly). At the same time, I was kinda interested into girls, but not really sexually. It all ended with me being completely asexual and celibate until I hit 23 and I deliberately chose to get the ball (omg, another sex pun....) rolling. Big mistake... After that, my libido skyrocketed and all what had been suppressed by workout and mental conditioning, erupted outwards and completely enslaved me. My body demanded sex, but my brain subconsciously resisted against me getting into male-female relationship. My body won...
Now, with the HRT my libido is down where it was in my teens and I am finally free. Also, as my body continues to change, I find myself being drawn towards guys more and more. I am not sure if I am ready for sexual relationship, but I very much enjoy communicating with them as a female - a little bit of flirting and teasing. Women now are like soulmates and I am not that much really sexually attracted to them anymore.
So, it is quite complicated at the moment and I am really looking forwards how this all will come together in the end.