Is it cool if your a gay guy dressing up like Victoria beckham and the guy your dating doesn't know your a guy?

Ok just this weekend I when to a bachelors party to dance with some girls and 2 of my girl friends joined with me with other 2 girls we don't really know so we dance and do dirty dancing in front of many guys and ion so happy that night that no one knows I'm a male coz I've been dieting for about 2 months just to look good with my outfit and I'm 5'7 tall, it came out really good that a lot of men cheer up while we dancing "Wannabe" a song of spice girls. later that night a guy came up to me to have a drink and asking my # to meet him the next day but I didn't not give him my # instead he gave his # to me. he keep on touching me in my back that night I even forgot that I'm a guy maybe I was a little drunk. should I tell him im not a girl before I go out and have sex with him?