Do things with him, get into a movie show, do some crazy stuff. Be spontaneous, I don't know how long you've been dating him. That's never happened to me and I've dated a girl for 3 years. To me it sounds like he isn't the right guy, but I could be totally wrong. Maybe one of y'all is tensing up about something. You could watch movies, don't have to talk about that, then after the movie you could bring up stuff. Sounds like a perfect relationship because most of the relationship is sexual or fighting, no need to talk. I've been dating this girl for one month and I've known her for 2 years. I would say you do run out of things, but for me its hard to get a conversation to start, but something will spark a conversation. Not to be sexist or anything but just talk his ear off, that's how all of Am do it. Just random sh*t with lots of details.