I understand what you're feeling, and I often feel like that myself. When I want to avoid a certain subject, I just try talking about something easier, something that has nothing to do with it. For instance, I talk about my studies. He knows what I'm doing most of the time, he knows I'm avoiding another subject but he just goes with it until I decide to talk about it again. Sometimes however, I'm not even able to do that, so I just stay silent, which is awful.
I hope things will get better for you.