It's very difficult to go into detail about this, but my partner pushed something a bit further sexually than we had agreed. (No, not anal). I asked what he was doing and he immediately stopped and apologised. This is a thing that we have done many times before and I only don't want to do it because of a specific (but possibly remote) medical risk.
This morning, he apologised as soon as he woke up. I challenged him on it (along the lines of 'this isn't what we agreed, why did you do that?') He kept repeating a reason that honestly doesn't make sense (basically he thought that it would be ok because it was adjacent to what was agreed and he thought that the medical risk was low). I eventually told him that his actions were scary and disappointing.
He has been a perfect boyfriend over the past year+ and is normally extremely respectful of my boundaries. Based on what he has said in the past, I have pretty firmly believed that he has a strong aversion to any sexual activity that isn't fully consensual.
I feel very upset about this and I am questioning everything I thought that I knew. He's currently very quiet and regretful seeming.