I often worry that I'm not acting gay enough. I'm always so worried I'm acting too straight, especially around those I'm interested in. It isn't until hacking my hair off that I was able to feel comfortable, even though I act pretty much the same I always have. I've always been the shy quiet girls, as you probably always have been the straight slightly effeminate guy. Gay and straight personalities are just huge generalizations within themselves, often formed around stereotypes. Be you and only you. Try not to worry so much about the opinions of others.
And as for the lady situation, I think you should just tell her. You could say something like, "I can't believe people think I'm gay! I mean, have you seen Beyonce?!" Well, maybe not the Beyonce bit.. Either way, good luck to you!