My boyfriend of four years wants to wear make-up to a lady gaga concert and a homemade skimpy outfit?

I am dating an obviously metro boy, but over the last couple months he is seeming more gay than metro and admittedly I'm upset. When he talks to people he doesn't know, he uses this gay "excited" voice and also when he works his retail job. He told me once that he "wouldn't mind being in a relationship with a guy" and since then these things really bother me. We have a very good relationship and rarely fight, he is attracted to me and I am attracted to him, but I cannot be attracted to him when he is being "gay". It is upsetting to me and makes me feel a little on the side. Also, I let him know that I'm uncomfortable with him wearing a skimpy outfit and makeup to the gaga concert (Admittedly I used very harsh words) but how insensitive he is to how uncomfortable it makes me to have gay guys checking him out like eye candy hurts my feels and makes me verbally puke words that are offensive and hurtful to him. I don't have a problem with gay people, I do have a problem with my boyfriend flaunting himself when he isn't available and it makes me aggressive. I'm hurt by this seemingly recent discovery, am I overreacting? What should I do?