How to ask him a question.

Sooo my bf and I don’t live together, and there are a lot of times we are apart. I think he chews. Which is not a problem for me, I just notice he hasn’t told me and he never does it in front of me. I’ve given him opportunities to tell me but he never does. We have been very intimate in sharing details with each other, so this wouldn’t be something that he should be afraid to tell me. How the heck do I bring it up... I feel like if I just blatantly ask he will blanch or redirect because he may not want me to judge him on it. Suggestions?