"I'm using it because you asked if I wanted to stop and I did. That's what it's for, isn't it? I've not done that wrong?"

It's at least half an honest question and he doesn't mean anything sharp with it. Instead of standing back up, he rolls back into sitting, knowing it's probably going to be a trial getting up again later and not worrying about that just now.

"You're not unable, I don't doubt you and never have. It's me; once I've seen that there's something bothering you its all I'm going to be able to think about, especially if it's bothering you enough that I even notice. I'm not unobservant but you've always been good at masking things so if I have noticed something then to my mind it must weigh heavily."

He reaches back to try and remove the collar, having difficulty with the buckle trying to do that backwards and without looking. He gives up after a moment, deciding to just deal with it for now. He shifts, distinctly uncomfortable in a way that doesn't just belong to the collar. "Tell me I've done something wrong if I have, but I didn't use my word lightly."