Five months pregnant and husband doesn't want sex ...

When we were first together we had sex quite often but the longer that we have been together it has slowly gone to nothing. He says he loves me and he's attracted to me but he is tired and works a lot which is true and he commutes to work and drives 3 to 4 hours a day so I understand that but what about the weekends on his day off still nothing. Is anybody else going through this to ? without any relationship issues just no sex? What do you think I should do to try to help us with these hormones I'm going crazy!!!