I would just talk about it. My best friend just went through a very similar situation. She had been working at Disney World, and met this guy that she thought was perfect for he. He seemed ridiculously nice and they had fun together, he went back home(Arizona) and they stayed together. She was supposed to visit him there in October and he asked her not to, she thought it was because of work. So it wasn't a big deal, he had a "friend" that he was always really concerned about and worried that she was doing things that weren't good for her, which is understandable. Well eventually she's playing around on myspace and finds pictures of them actually kissing on there. And that's just not cool. She said if they had just been kissing it wouldn't have been a big deal because she'd been making out with one of her friends for a while and not telling him about it, but he had the audacity to get into a relationship with this other girl while they were supposed to be together still. They ended up breaking up but that was for the best. I mean you've talked to him, and I understand that feeling there are things my boyfriend doesn't tell me just because he doesn't think about it. But when I do find out I usually flip out. It would be better if they would just tell us and not try to hide things.
This post has gotten way to long I'm quitting!