why are you staying in this relationship? It's not nourishing (for either of you) and adding to the sum of misery in the world, not its joy.
You have no children: there is no earthly reason why either of you have to suffer and "make it work".
when you are both dead, there will be nothing and no-one standing by your graves, commending you for wading through misery like this.
Sorry if that sounds harsh to your ears but it is true. I don't mean it to be harsh - it's just that it is such a waste of your life to do this.
There is absolutely, completely and utterly no point to this. Even staying to try and work out who is "at fault" and "responsible" for all this misery is pointless.
Really. Sometimes it is just best to shake hands, say "We tried. Let's try again, with other people." - and leave.
And yes, I too think you sound depressed. The thing to do is to go to the GP, get started on sorting that out, and then, when you are in a better place, reflect on what went wrong, and gather some life lessons from it.