Pretty sure my marriage is almost over

My husband and I have been at each other’s throats for going on three weeks now. He is so mean at times it’s crazy. we haven’t had sex in almost 3 weeks because of this. We planned to do it tonight but I asked for a back rub and he said no so I said I wasn’t going to give him head. If he can’t put forth any effort why should I? Then he said fine then I guess we don’t have to have sex. He rolled over and went to sleep. This isn’t my husband. The man I married was borerline sex addicted. I don’t know if he’s met someone else or what but I’m almost sick thinking about it. It’s like he just doesn’t find me attractive anymore. I mean I get it. I’m heavier than I used to be but I’ve had two kids both via c-section. I’m trying to get back into shape but it’s been really really hard. I’ve tried to talk to him and he just shuts me down and tells me that I’ve been stressing him out. I don’t even know how I’ve been doing it and when I ask he says it’s the fact that I have asked to go back part time when I go back to work from my 12 week maternity leave here in a couple weeks. I don’t know what to do but I really feel like my marriage is over. He isn’t even trying anymore.