stress management

My boyfriend is too stressed out to have sex. What can I do?

I'm 21 and I've been in a relationship with my boyfriend for two and a half years now. We go to the same university and have practically been living together in the same on-campus apartment for one and a half years. As our relationship has progressed, we've begun to have less and less sex. Neither of us initiates because we're always tired or stressed out....