My bf keeps breaking up with me over sex

We have a very weird dynamic, our relationship is really good and love is strong, he is a wonderful man and best friend, we respect each other and live normally, but he wants more sex in a relationship. I like him lots and our sex is always really good, but he always goes through this phase where he says he can’t be with me anymore and he has to find a woman who’s more sexual than me, but after weeks of him telling me he can’t be with me anymore, he always takes it back and says he doesn’t want to break up. I feel worthless honestly, I feel like he only wants me for sex and that I am nothing without my body to him. What do I do?