Need help

What to do when you don’t know if your husband is suffering from a mental breakdown or just affair symptoms? He came home from deployment acting like a complete stranger. I found out he had an affair, still unclear exactly who it is but a girl in Europe along with someone at his work. He will say things and then tell me he didn’t say that hours later. He wont see the kids on Christmas and he’s always been a family man. Saying I’m super evil and im the cause of his ptsd. On deployment we fought a lot. He called me one day to say that he was thinking of all the bad things I did to him over and over. Our marriage was full of ups and downs. I’m not sure if that’s when the ptsd started. He works in mental health and I know he was burnt out from the heavy topics with soldiers. He also did talk space on the side. He got on new anti depressants. I think he might be experiencing a break down. He keeps acting more erratic. Secondary trauma from hearing about things maybe? I’m just so concerned and now we are going through a pending divorce he wanted the day he got home. Wouldn’t listen to our kids or his family at all. Or me. He cried to me and said he felt so broken inside. That I’m the cause of his ptsd nothing else. I’m just so torn. Anytime I talk he says I’m gaslighting. I’m evil. I just am at a loss on what to do.