If this is just a recent problem, there might definitely be a dental problem, either a rotting tooth or some other problem that could be fixed. I think that you and your boyfriend should be able to be comfortable communicating and talking about things like this. I would bring it up in a very nice way, just saying that this is a very recent thing, and you have no idea why, but you have notices that he has really bad breath. You can say that maybe there might be a problem with a tooth or something, and that maybe he should get checked out by a dentist. In the mean time, you can ask him to use some Listerine, chew gum, or eat some mints. Just tell him that you don't want anything to get in the way of you wanting to be near him... I think he'll understand. It's not like he did something wrong. Things like this just happen.
