past/ future relationships

I've been So hurt.. cheated on, beat, treated so poorly in past relationships I feel like the man I'm with now will eventually turn into that and it scares me. I have no clue how to get over the fear. Over the insecurities and trust issues. He's a good man, but I can't trust him, and always think something is going on or that he's going to leave me. Can anyone give me some advice