I am and have always been in heterosexual relationships, to the outside world that is anyone sees. But when I was 18 I wanted to explore my curiosity of being with another guy. I met a guy on craigslist who was twice my age but lived close, and was hot.
I met him at his house, he said he wanted me to experience what it was like to feel like a girl. I let him shave me from the neck down (my face was already clean shaven), lock me in chastity, dress me up like a girl in lacy lingere, panties, bra, garter, stockings, and a summer dress. I already had long hair so he styled it and put makeup on me, I really looked like a girl by the end. I won’t go into all the details here but he did as he promised and made me feel like girl on prom night. This went on for about a week.
It was a great week, learned a lot about femininity through experience which I think helped make me a better partner today. On the gender spectrum I am male, no ambiguity there. It might have been just a kink thing, maybe mixed with some curiosity and desire to experience what it was like to be the more submissive partner.