CW: Discussing sex, though doing my best to keep it not too graphic

I posted about this a few days ago in another forum and several people there (and friends since) told me it sounds like assault; I hadn't even considered that until people started telling me. I'm hoping maybe to get some feedback here. I've already ended the relationship. I'm just trying to process what happened.

I had been seeing someone, and we decided to sleep together last week. We talked a lot about what we would do beforehand, and it felt safe. I explicitly told him that I was only recently bi, so I'm not very experienced with oral sex, and he agreed to help teach me. When we got to that part of the evening, though, he grabbed me so that i was unable to move and immediately went so deep that I couldn't breathe and started choking. He let up eventually, but as soon as I caught my breath, did it again and kept doing it until I threw up. It was rough enough that I was unable to eat solid food for almost all of the following day, my throat hurt so much.

I had a safeword and didn't use it. I'm kicking myself, but I was so thrown off and confused and also embarrassed because of my lack of experience. I feel like if I had used it, he probably would have stopped. But I've talked to several people who are saying that I shouldn't have had to safeword--what he did wasn't ok in the first place because it was so much more violent than what we had agreed on beforehand and he should have stopped long before I threw up.

The whole rest of the evening, he seemed kind and considerate and concerned for my wellbeing. But I've been having flashbacks and panic attacks extensively around this. Is there a way that this could be considered assault even if he didn't intentionally mean to assault me but was just being thoughtless and inconsiderate? Like I said, I'm not going to see him again because of the emotional toll this is taking. But I'd like to figure this out just for my own sake.

I'm really mad because I had finally got to a place after my last relationship where I was trusting people again. And sometimes I don't know whether I'm reacting because of past abusive relationships or because I'm in a current one.