What should I do

I recently got back from a month long trip away from my boyfriend and we were talking about having sex a few times while I was there. If I teased him he would get hard very quickly and jokingly saying how he wished he could share it with me. Now that I’m back and we’ve been trying to have sex, he can’t get hard. This has happened twice already and happened once before I left. I know that he feels bad but I don’t know what I should say to him or what I should do.