Afraid to call the cops.

Sometimes. Very rarely. My boyfriend puts his hands on me. Just grabs me aggressively and grips my neck hard and holds me down hard. Stuff like that. I fight back the only way I can with my nails. I’m only 5ft. And he’s 6ft 1. So a lot bigger than me. I threaten to call the cops but he says he will show the cops the Scratches on his arms and I will be the one to get arrested instead. I feel stuck when this happens. What do I do ?