I'd disagree with some of the posters here about depression. From personal experience it can manifest in many ways and many depressed people (men in particular) can "banter" and act relatively normal "in company" only to act very diferrent at home. It's very frustrating and if you Google this it's incredibly common.
Symptoms of depression in men can often include unexpected things like irritability, blaming, anger, manipulative behavior, verbal abuse, affair seeking, porn use, heavy drinking, bad sleep.
Depressed men can sometimes fit the picture we have in our mind of "depression" (the crying, hopeless man laying on the sofa all day with no energy) but it doesn't always present like that. Sometimes you just experience the person changing into an irritable, nasty person and then it's hard for anyone but the person in it to see how much their partner has changed.
If he is depressed and wants to direct blame at you then nothing you say or do is likely to adjust this opinion. He will want to continue with this opinion because it's far easier to blame an external source for feeling shitty than it is to look any deeper.
The best thing you can do is leave him to it. Go and get you own place and let him work through how he feels on his own. If might be that he is depressed and it might be that he is not. Even GPs can struggle with diagnosis on this sort of stuff. I got diagnosed with severe depression once when I was not remotely depressed. I'd direct him to a few leaflets or websites on depression and leave him to it. If he is depressed he will probably fall down to rock bottom before he admits he has a problem.
It sort of doesn't make a difference though if he's not able to face it and get help. The facts are he is treating you badly and blaming you for his unhappiness. Depressed or not that's clearly not okay.
I'd recommend buying the books by Anne Sheffield, available online, and perhaps talking to your own GP yourself for some advice.