How do I tell my boyfriend to back off in a nice way because he play fights to much?

I don't wanna hurt his feelings but he is just play fighting and hurting me to much, I don't know hiow to tell him in a nice way to back off and stop hurting me. Even my parents have noticed that when he comes over he play fights excessively, they can see it annoys me. He's a red belt in kickboxing therefor its so easy for him to hurt me and he kind of has ADHD, so I know those things arent a good mix. I love him a lot but I just want him to stop, but how do I tell him this?