Emotionally Abusive Relationship

I'm scared I'm in an emotionally abusive relationship, but I don't know how to get out of it because every time I leave he comes back to me, swears it'll be different, promises me the world, and I'm stupid enough to go back. He won't leave me alone even after I have moved on. I don't know what to do. Has anyone here ever been in a relationship where you felt your partner degraded or belittled you? How did you get out of it?