if you have sex with a man dressed as a woman but not at any other time than you are not gay.
Gay men like having sex as men and like being men.
My therapist, and I had 4 total all asked me (when I asked them if I was gay),
if I felt like a man or a woman when with these men I had sex with, I told them that there was nothing male about the way I felt or acted and gay porn does nothing for me but I am attracted to men as a woman never a man.
they said I'm not gay, because I did not identify as a man when with these men.
So there is your answer, you can have sex with a man and not be gay providing you do not see your self as a man having sex with a man.
If I have sex with a woman I still feel like a female so that makes me a lesbian in a male body.