Husband won't have sex with me

I'm 25 weeks pregnant with our third child and my husband has stopped having sex with me or even initiating anything. We've fought about this multiple times but nothing ever changes. I have to literally cry & beg to get it once a week. I'm beginning to think he may be having an affair. I caught him messaging another girl about a month ago.

I feel fat & ugly being rejected constantly is breaking my spirit. I feel alone in my marriage. Sorry for venting. I was just rejected again tonight.