Husband won't have sex...

After my 2 month mark of being pregnant my husband stopped wanting sex. I was always hinting at it and trying to make a move but he was never in the mood. Now I am 6 months pregnant and we haven't had sex in 4 months. I tried to talk to him about it ONCE and he got upset saying it was his fault he doesn't have a sex drive. He didnt want to talk about it and said he was really embarrassed. He won't admit if it has anything to do with my pregnancy. Anyone else having a similar problem? Or for those of you who have been pregnant before, does his sex drive come back after birth? I don't know if I should be concerned or if it's normal.