Talk to him. If he's understanding like you say, then he will be there for you. Explain that you don't have a sex drive right now, and explain that hormones are making you react in unexpected and sometimes unfair ways. It's better to talk about these things than to hold any tension. My partner didn't mention when he was upset and I took for granted that everything was fine, until he blew up and I realized that our lack of sex and the stress of becoming a father were actually bothering him. If we had talked about it earlier, there wouldn't have been a need for flipping out.
Im sorry hun i wish i had advice. Hormones can suck!