My bf says he sometimes think about other girls naked that are his friends or people he knows at school. When he is alone or when we have sex.

He said at first it was just completely intrusive thoughts but now that it’s more or less intentional. I don’t know what to do. He also told me he realized his type and it’s brown girls with small boobs and I’m white with bigger boobs. I feel so disrespected by this. I completely understand him seeing people and thinking they are attractive and all that but this ? This is too much… what should I do? And is this normal?