Hello @xorsted, welcome to the Forums. It sounds like you've been through a great deal within your relationship. The fact that you've managed to keep looking after your children and maintain employment is amazing. Your resilience may well have run out as you've been spending it on looking after everyone else and doing the right thing by your employer! We're a bit like cars that way, if you don't refuel it all grinds to a halt.
Sometimes when we feel overwhelmed it's good to remember what we can actually control. Your husband is receiving treatment that will hopefully start to make a difference soon. But either way, his health is beyond your control. You've hit the inevitable place where you know deep down that you can't continue without more support for yourself. The scales are just too far out of balance. But this bit you can control.
So even though you won't feel like you have time, you really do need to invest in yourself. That might be a referral to a psychologist from your GP. Or it could be giving yourself permission to do more for yourself - like hang out with people you enjoy but don't feel responsible for. Or go for a walk with an audio book so you have a break from thinking about all this. Book a couple of days leave from work to spend how you want.
When we're drowning in our responsibilities this feels impossible. So you need to start small and think about it as essential maintenance
It's been a few days since you posted. How are you feeling now?