Is this where it all begins? [F38] and [M39]

My boyfriend [39m] and I [38f] have been acquaintances for a couple of years, but we've only been in a serious relationship for about four months. One night, during an argument, things escalated beyond what I'm comfortable with. He tends to express himself with animated hand gestures, and in his anger, he was poking at my chest and flicking me while he was talking. I had never seen him behave like this before, and I felt it was best to call it a night so we could both have some time to cool off. Unfortunately, that decision led to a situation where he angrily urged me to leave but also blocked the door. Normally, I would have walked away from anyone who spoke to me in that manner, but instead, I stayed. At that moment, I realized, oh no, this is how unhealthy relationships can start. Until that night, he had been wonderful, and then it felt like everything changed in an instant. The night included him grabbing my wrists, tossing me onto the bed, and head-butting me. While he wasn't using his full strength, I could have been hurt easily. Each time he did something aggressive, he insisted, "I didn't hurt you!" I've never really doubted myself before, but now I find myself questioning if I'm overreacting. Deep down, I know I'm not, but this sudden self-doubt is even more concerning. There was also an earlier incident where my hand got hurt, but again I found myself dismissing it as just a jammed finger, thinking I was overreacting. I've tried to talk to him about my worries, but he quickly becomes defensive and insists that he's not the type of person who would hurt women.