Most Helpful Guy
Peace of mind is a creation of your own mind. He cannot provide it for you.
What he can do, however is provide a level of support where peace of mind becomes attainable. If you don't think he's capable of this or you've told him this much and he's still not trying, then I'd say build up your self-esteem, solo.
Just make sure to be honest with him.
With that information in-mind he'll either focus on improving himself for the better or return to where his thoughts had been lingering all along.
Most Helpful Girl
It sucks to feel that way, I totally understand. I've been through the same thing. You have to stay true to yourself. If you feel like you are not the person you used to be, you should think whether you should stay with him or not. I wouldn't, personally. Trust is very important in a relationship.