Haha, this is like looking in a mirror.
I'm straight, but I certainly do prefer lesbian porn to most others. I don't really see what sort of a link that has with being bi-sexual. Funnily enough, people are sometimes confused about my sexuality because of how comfortable I am with physical contact, both guys and girls. But that hardly makes me bi. It's as much a thought process as anything else, as I so poorly phrased it when discussing this the other night:
"It's like, you look at a girl and think 'I would!', but I don't feel that when I look at a guy, I find myself comparing myself to him, but that's more because of how f****** insecure I am but it's really not the same. I mean, I've kissed guys before, but it's not the same at all to be honest, not least for the awkwardness. People describe it as a 'spark', well I don't know if it'd ever really call that feeling a spark, but it's more like a feeling that something's intrinsically right when I kiss a girl, you know? It's almost as though everything I was worrying about and everything I was fretting over just sort of slips away... On the two occasions I have kissed guys, it's nothing like that, no feeling; just an awkward feeling of self-consciousness..."
That's a quote straight from my MSN chat log, but it kind of makes the point. You know whether you're straight or gay or bi. When you really get down to it, it becomes really obvious to you. As for the actual kissing guys, one of those was on a dare a long while back, another was on a forefit for not doing a dare. Neither really by choice, but rather as part of the game (although certain people will never let me live that sort of thing down...)
To be honest, I don't think either of those signs would indicate that he's bi, or more into guys than girls. I know straight girls who prefer lesbian porn, and straight guys who also prefer lesbian porn. I know straight guys who make wall to wall gay jokes (perhaps myself included), but that doesn't really indicate anything, especially if they're drunk when they're doing it.
One simple way to look at it is that he's your boyfriend. If he was more into guys, surely he'd be dating a guy and not you. As a good friend of mine so aptly said "Well, I don't really see the difference when you're dating a guy who's bi or straight, I mean, they're into girls either way anyway, so it's just a matter of how good a fashion sense they have..."
Hope that gives you some sort of an insight...