Decreased sex drive question.

I'm 10 weeks pregnant, before we got pregnant we had sex twice a week, and in early pregnancy it decreased to once a week. Now we are only having sex once every two weeks. I'm not ever horny, and don't really want to have sex, but I haven't told my husband that, I just haven't been initiating it. My husband doesn't really seem to mind that we are having less sex, as he isn't initiating it either. Even though I don't want to have sex, I still want my husband to want to have sex with me. I asked him if he's lost interest and he said no. What have you ladies been experiencing, and what is your opinion on why a husband would lose interest in sex?