Obsessed with getting a new car

Laura • Due March 2020 with #2
I want to slap my SO. We've carefully planned out our savings and debt payments so that I can stay home after baby is born in Feb. This includes already paying off our cars which are both two doors. Currently we plan on trading in my car for a small suv and paying the difference in cash. But he wants a new truck so bad, that he now plans on us both getting new cars, which would mean taking on a car payment. I thought we were in the same page but he has an attitude about this now. Why can't he just wait a few months so we can save up some money?? Errrrrrrrrr!!!!! He's annoying the shit out of me in general too - I'm hoping it's just the hormones...