I, myself, rarely bring my girl to clubs, but, as a friend of guys who are like your b/f, it's not a question of jealousy at all and it has nothing to do with it. It's sad but most guys I know do what your guy is doing for the reason that having a sexy girl half-naked on the floor with you is kind of an ego-booster, a trophy you could say. It's like saying look at me, I'm with "something" you want, yuou envy me, etc. It's basically an ego thing. Well, that's my take on it as well as several other people I know.