I'm tired of hearing about HER

Okay, so my boyfriend and I have been friends for a very long time. His ex was HORRIBLE to him and since they broke up, she has continued to try to make his life a living hell. I know it bothers him, but I feel like every conversation veers toward her and all the problems they had. I told him today that I want him to just stop living in the past and be happy with me, and he just got so angry. What do I do to get his mind off of them and back on US? 😔