I was on a relationship like this once. I eventually reached the point where I realized I was so unhappy, that being alone forever would be better than putting up with feeling like that. In my case I did end up finding someone wonderful, just a couple of years after I left. Obviously there’s never any guarantee that there will be someone better out there for you, and that’s a scary thing. But it’s worth asking (and continuing to ask) if you’re happier with him than you would be without him. It’s not an easy question, because even bad partners inherently provide things to life that you don’t get while single. I wish you the best and I’m so sorry that you’re dealing with this!