Sexual Assault?

I was at my boyfriend's house and something happened but I'm not sure if it was assault or not. We were sexually active but I told him that I didn't want to do anything that day several times. He decided that he could change his mind by pushing me down on his bed and making out with me while I just laid there and didn't move. He exposed my breasts and started kissing them as well and he was grinding on me, hard. I told him I didn't want it and moved my head but he just kept going. Eventually he stopped before any penetration of any sort occurred which is why I don't know if it counts as assault, or if it's anything at all because he's my boyfriend. I was wearing jeans and I've been thinking...what if I'd been wearing a skirt? Where would it have stopped then? Idk it just makes me so nervous. Was it sexual assault? And what should I do if it was?