Oh my god sweetie, that is a difficult question. How long have you two been dating and how long is the distance between you guys?
Okay, I’m gonna assume that this guy is absolutely terrifying and would go crazy if you left him. The first thing you have to do is get yourself somewhere SAFE. When you do it or just a little bit after, get somewhere that he doesn’t know about. A friend’s house, a relatives, anywhere. Hell, if you wanna travel to Mexico for a while, you are welcomed to stay with me, my home is your home.
The one thing you have to do, is be firm. Don’t scare away and be strong with your words. Tell him that as sorry as you are, you simply can’t continue in that relationship.
If he does try to pull something and you are aware of this, PLEASE don’t hesitate in calling someone. Even if it isn’t the police, at least call your parents or your buff friends. Don’t be alone. You can do this okay? This one relationship will not end your life. I believe in you okay? /hugs please keep me updated.