Most Helpful Girl
Good luck. Buy her a dental kit
Most Helpful Guys
Good luck. Just say it to him. You're interested in continuing with him but there's something that's bothering you, and talk with him through it you know.. It'll be hard yes and he may not even be at fault but. Try.
If the chewing gum did not make a difference then the smell is either coming from his tonsils or throat. It could be tonsil stones, bacteria at the back of the throat, or also an area near the wisdom tooth that collects food that putrefies.
If the smell was coming from his tongue or mouth, then the chewing gum may have helped. The problem is that he won't know unless someone tells him because most methods of smelling your own breath do not work as you probably know.
The problem is likely to be deeper than simply brushing and flossing, especially if it's tonsil stones.
Having said that, the most sensitive way to approach this would be to list all of the things you just said, everything you love about them, then say how much you feel honesty is a good foundation and then lead on to talking about the breath. However, the problem is that you've only just started seeing him.
Either you tell him and be honest, or you resent him and eventually leave, one outcome has potential, one does not. Choose one.