not sure how to feel

so my boyfriend and i have been together for 7 years and it has been great we are expecting our first next month but we havent had sex in at least a month and its weird we went from having sex all the time to never when I ask him about it he says its just different I get that I'm bigger now but does he just not find me attractive anymore or does it actually feel different to have sex with someone who is 8 months pregnant and should I be worried about him cheating he a got to be getting it somewhere to not even want a hand job from me maybe my hormones are just going crazy but I feel like something is definitely off