sexually assaulted by significant other

Hendrica
2 days ago I got sexually assaulted by a guy who I've known for years and trusted and also have feelings for. I hate to think that it was sexual assault but I know that's what it was. 
I told him dozens of times that I didn't want to have penetrative sex as I had just started my period and wasn't comfortable but was okay with oral sex and non-penetrative play. But he forced me face down on the bed and proceeded to pull my pants off and attempt anal sex despite me saying no and telling him to stop; only stopping once I started screaming and crying. 
I don't know what to do now, he seemed surprised at my distress and tried to comfort me. He apologised yesterday and promised it wouldn't happen again. I want to trust him but I don't know if I can anymore. I was so scared. But now I'm scared of losing him. Why am I not mad at him. I feel like it's my fault.