How is what your boyfriend is doing any different to any kind of relationship (homosexual or otherwise)? Are you trying to bullshit us and say that you've never fantasized when you've seen a hot guy walked by? Don't make me laugh. Everyone fantasizes. It only becomes a problem when they choose to act on it. If you're going to get this bent out of shape just because your boyfriend fantasizes about guys he's never gonna meet much less lay a hand on then you're not cut out for relationships, kiddo. Leave it to the pros.