Blah.

So when my husband and I first started having sex we could go all night or two times a day. Within the past few months he can hardly keep it up. We have sex he cums an he gets up. I don't understand. And he won't want to do it but maybe once a week. Twice if I'm lucky. I get so frusterated. He can't be worried I will get pregnant cause I take birth control. I am extremely good at taking it at the same time every single day. Any advice.?