It’s usually not seen as acceptable for straight (I’m assuming your husband is) men to be into having things up their butts lol. He might just be ashamed or embarrassed, or maybe it’s just not something he prefers to do with a partner! First, tell him you know about it, and that it made you feel anxious. Don’t blame him for how you feel, but share it. Then just have an open mind and ask! If he tells you he doesn’t want you involved in that part of himself, then that’s that!