What the others said, about not screwing up the friendship, is very important. He may also be teasing you, if he knows you are gay, by flirting with you. Straight male friends will do that sometimes, as a joke, or as part of an ego thing where they KNOW they turn on gay guys. One fairly easy way to deal with this, is to tease back---flirt back. Call his bluff. More than likely he'll back down and stop the teasing. If he takes it forward, then sit him down, tell him you would love to, but not at the cost of your friendship, that your friendship means much more to you than just having sex, and you would rather give up the sex than screw up the friendship. Make him think about it a little, and consider the consequences. Whatever happens, respect his wishes. Also, consider the feelings of his girlfriend. Some guys feel that it isn't cheating on their girlfriends, if it is with another guy. Most women feel very differently---that is it much WORSE cheating with a guy, because they can compete with another woman, but how can they compete with another guy? They feel betrayed, and lied to, and often, very used. If they have a good relationship, and it looks like they might go somewhere with it, back off, and let him know you ae flattered, but you would fell very bad if it messed up their relationship, and you respect him and love him too much as a friend to do that. Those are my two cents, anyway. Good luck with whatever decisions you make.
