I'm ttc and I'm ovulating this week and hubby doesn't seem interested in sex. I know I can't force…

I'm ttc and I'm ovulating this week and hubby doesn't seem interested in sex. I know I can't force him to have sex, and when I talk to him about it, he just says "it will happen when it happens" .... he's the one who brought up having another baby to begin with... I'm just lost because I thought we would try every month, we have been having fun with it so I don't know what's wrong.