Use sorting the house out as a free work out that has to be done - work up a sweat if you can. Scrub, carry things upstairs, squats to pick things up. Treat it as a real job.
Start small don’t do yourself an injury.
Fill your bin each time it is collected, broken electronics and batteries aside anything that can be broken down and fit in a bin can be thrown away.
Totally agree with declutter.
Think about your life now, not what you envision, just what it is now.
What do you actually need? What do you need to do?
The two things that leapt out is your health and the kids.
So what else is taking up space?
A clear, calmer, calm-ish home might calm emotions down.
Can you remove things that break being thrown downstairs from eldest’s room? So leave soft toys, any books, clothes. Keep the breakable toys/tech downstairs?
Take sometime outside just to breath with a drink. Just in the garden our outside your front door, with a drink, 10 minutes after morning school run, not to think about anything you have to do but just to be, a bit like meditation but not meditation (I don’t think if you have mental difficulties that meditation is a good idea without supervision) but just to just notice what you can hear, see, feel, smell. It doesn’t have to be countryside perfect surrounds, can be traffic, clouds, cool breeze, police siren, doesn’t matter as long as you just spend 10 minutes just noticing before you come back to your what needs doing life.
Small changes, very small changes, that stick are much better than huge sweeping changes that burn you out.
Also use the nice shower gel, or best glasses for water, every day. Check out the tatty stuff.
And drink water. Your body and brain works better when hydrated.
And never give yourself a hard time if what you planned to get done doesn’t there is always tomorrow.