How long should I wait?

I have no problem with my husband watching some porn, as long as it doesn’t affect our sex life. We haven’t had sex in probably 5 months now. He was saying due to stress at work and vacations and a big move. Well yesterday he was joking and making a weird comparison about my sweet tooth to his porn addiction. I knew he watched occasionally, but there was something about the way he said it. I asked him how often and he refused to answer. Saying he didn’t want to talk about it wasn’t any of my business. I could tell he was too embarrassed to answer. Or maybe he didn’t want to hurt my feelings, I don’t know. Anyways, my question is how long should I wait before asking again? Clearly it’s a sensitive subject so I don’t want to push too hard, but I know I deserve an answer.