Idk what he's trying to do, but it doesn't take a genius to figure out when your partner distrusts you. Especially when 2 people are close, reading eachother becomes second nature.
For example, I have borderline and my bf knows when I'm trippin ballz before I do. In the midst of my denial, if I have the good sense to stop and think, then I will admit that yes, he saw where that was headed and I need to breath, calm down, and listen to facts instead of act out on x,y,z feelings for no good reason.
So yes, sometimes someone else knows us way better than we'd like to think they do.
Also distrust shows whether you want it to or not, and with all this interrogating regarding his masturbatory habits, its no wonder he knows what you're thinking.
You didn't twist your words, don't feel bad, I just don't have any answers and that's why I didn't respond when I first read it.