What counts as sexual assault?

I few months ago, I went to a friend’s house, let’s call him Nate. Nate and I had been friends for quite a bit at that point and he was one of my best friends so I trusted him, entirely. So, we were hanging out, joking around, and he just sort of gropes me, sticking his hands under my shirt and grabbing my breasts, which I dismiss as banter, or just his general behaviour. Fast forward about 4 months, where I’m at his house again. We were lying in bed, napping and laughing because we were overtired. All of a sudden, with no initiation or invitation from my part, Nate kissed me. I told him to stop, and pulled away. I sat up in the bed for a while, hoping he would let it go, but when I laid back down, he did it again, all but trapping my face between his hands and I almost had to punch him to get him off of me, and I left the room and joined some other people that were there, out of fear of being alone in a room with him. Ever since I’ve been feeling really empty, jumpy and on edge. Sometimes, I even wake up with nightmares about it. I just decided that since nothing r e a l l y happened, it didn’t really matter. Which made me feel like I didn’t really matter. I googled what is defined as sexual assault, but I couldn’t find anything that clearly stated whether or not it was. Don’t get me wrong, I know it’s more complicated than that, I just feel so lost. Ever since then I can’t handle people touching the area where jaw meets neck either. So, basically I’m just wondering whether or not this was sexual assault or if I’m just being dramatic. Thanks <3