Should I finally accept that my bf did sexually assault me?

I’m utterly distraught. I don’t know what’s real and what’s not. I have severe OCD which has (in part) focussed on a fear of being sexually assaulted by my (25F) boyfriend (26M) after a stranger SA’d me in the street. I’ve analysed every sexual interaction I’ve had with my boyfriend and this particular incident just feels too bad to be “just” OCD. If this is really, truly assault, I’ll have to break up with him and reevaluate our entire relationship.

Around 3 years ago, I went through a phase of stopping halfway through sex a lot due to anxiety. One of these times, we had just stopped and my boyfriend lovingly said to me “don’t worry, we don’t have to do anything you’re not comfortable with” and we begun cuddling naked in bed together, pressed very close. We chatted for a little while about my anxiety and my boyfriend asked me in a caring and concerned way “do you think I’m too sexual sometimes with you?”. I begun to answer and after a few moments I begun to feel some very gentle movements down below. It felt like he was adjusting himself because he was uncomfortable or something, so I glanced down and my boyfriend had his hand on his penis and had been very gently moving it back and forth so it brushed on my vulva.

I said “what are you doing?” and he glanced down and said “just stroking you”. Immediately panicked and completely horrified, I got up and left his house. I almost broke up with him that day. Later on I made him explain what the fuck had been going through his head. He said he was doing it absentmindedly, not thinking at all and certainly not thinking about the fact we had just stopped having sex and I was so anxious. When I asked him to explain why he said the “stroking you” bit (because it made him sound like he knew what he was doing) he said he had attributed an understanding of what he was doing after the fact - he looked down, realised what he’d been doing and said it out loud.

I am convinced of his lack of thinking/absentmindedness - he is a very sincere person and would not lie about this. I think he was physically still very turned on from the sex and had acted on a feeling with little to no thought whatsoever. The fact we were having that conversation and he was being so loving and caring prior to this also points to the fact it was not intentional.

However, he must’ve been getting some sexual satisfaction from this action and according to the definition it is sexual assault. The action was not wanted and therefore non-consensual. I’ve analysed this event on and off throughout the years and it has been a source of huge anxiety for me - this idea that he DID assault me. I’ll add he has not done this since and has been very respectful of my boundaries.

Please, please help me. Should I leave him? Did he assault me?