How to compete with the fantasies of previous sexual partners?

This isn’t my first post and it seems my boyfriends addiction has kind of changed shape as I’ve done more research over time. He has stopped, or at least promised me, which I do believe, all porn. The issue is he fantasizes about previous women he’s slept with and those experiences and only that arouses him. I can literally walk around naked, do all sorts of bedroom tricks and cannot turn him on. Each time I feel more and more insecure. How do I compete with these thoughts? I know the over exposure to porn has given him a messed up view on what sex should be like with a partner and he can’t see it as an act of intimacy between people who love each other.