I am having a somehow similar, yet different experience.
My whole life I thought I am attracted to women (I was even married in an arranged marriage at 18, but I would not count this in any way). In the last years I dated several women, and with ALL of them I had the same experience:
We would go on a few dates, I would love it, we would make out (hence, I usually liked the touching part more than the kissing). Then after a few dates we would get intimate in bed. The second that happened, and I found myself in the male role in bed, I got turned off, and it was over.
This happened with each and every girl I was dating.
Finally my therapist helped me realize that I might have never been sexually attracted to girls, I just wanted to be like them.
However, I was never attracted to men. But since I came to terms with myself being a girl, I can see myself being intimate with men, when I am the girl. But even now when I look on guys, I don't find them that attractive in a sexual way. I just started Hrt and am waiting to see if anything will change (in studies, about a third of trans women reported a shift in their sexuality just a few months after being on hrt).
At the same time I can see myself being sexually involved with girls, as in a lesbian relationship, but not if I am the male in the relationship.