Trust Issues

I have the best boyfriend. He is understading, patient and just the best. But i cant get past my trust issues. Before him, i was in a very unhealthy relationship. I went thru a lot and was very miserable. That relationship left me in a dark place. & sometimes i take it out on my current boyfriend. And i know it is not right, but i cant let the past go. & i feel like is messing up my relationship.