Messycow - I know exactly where you are coming from. I had the same problem. But a tidier house helps you to feel better, so it is really worth getting it sorted. Have you seen your GP or HV about the PND? I take AD's now, and they have helped enormously.
Anyway,
Kitchen - pile up all the dishes in order - plates, bowls, glasses. Put all the cutlery in a big jug with hot water and washing up liquid to soak. Then just tackle it a pile at a time. Wipe the sides down while loads are drying.
Washing - get all the washing from everywhere, and sort into loads of darks, whites, lights, colours etc. Then put each pile into a bin liner and wash in order. Just work your way through it. Tumble anything you can if you've got a drier. Put heavy things on the line (towels) if it's sunny. You can even put your airer outside if it's not too windy.
Mess - go round with a bin liner, and pick up all the rubbish. Then go round with another one, and throw everything into it. Then you can at least hoover. A clear clean floor feels a lot better.
Dust - as much as possible with hoover. Then wipe sides with a baby wipe.
Mopping - hoover first, then brush, then mop. Do everywhere in one go, so you're not spending ages getting all the equipment out for one room.
Could you afford to get a cleaner at all? Perhaps knowing somebody was coming in once a week would motivate you to tidy up so they could clean? Perhaps a friend could suggest somebody, or you could contact an agency. Even if it's just short term for a month or two, it might help you get back on track. It's easier to walk a flat path than climb a mountain.