Why doesn’t he want to?

My boyfriend and I have been dating for 7 months now. We both were into each other at the same time so I know that our relationship is mutual and we are still very happy together, but he does not want to have sex.

The weird past about this is he wants to do other things, everything that’s sexual that would lead us to have sex but when we get to that point he won’t go any further

He is also not a virgin and has been with several different people (past relationship, which were safe) but says he just doesn’t want to and keeps saying “I don’t know” when I ask him why or ask him about it. He has told me several times he really wanted to but just won’t.

Can someone explain maybe why or if this has happened? Should I let it bother me or should I just let it go & wait for him