I thought I was moving forward but this has shocked me

Can the children with special needs get DLA? If they get middle or higher payment you might be able to claim carer's allowance. Are you claiming working tax credits? Can you get housing benefit? Make sure you get someone from Social Servicers to do a check for you to make sure you are claiming everything you can and also to calculate how much you could claim if you did not work at all. Sometimes if people are low paid and in work it turns out they could get more if they stayed at home and do nor go out to work. Looking on the bright side maybe you could charge a foreign language student a little less and they also do a bit of cleaning for you. If you have anyone who can support you emotionally, do not be too proud to ask for help. Even if you are divorced form your ex h he is still the children's father and should help with care especially for SN children. I hope you feel better soon.

Mumx5 This is awful. Please see Citizens Advice in your area.

So sorry to hear your story.
On the practical side have you checked that you're getting all the benefits you're entitled to? Can you get any support -financial or emotional from your grown-up children?
A visit to your doctor might help, you must look after your own health and well-being before you can look after any one else.
My best wishes go out to you.