Being so hard on the OP isn’t helpful.
The reality is that there are millions of children in the UK who have a hand in caring for their parents, and some of those are of primary age. This is why the likes of young carers exist.
The situation is absolutely not ideal, but to accuse the OP of neglect is a step too far. The children shouldn’t be in the house caring for other children and if the school got wind of this then it’s possible they would make referrals accordingly.
However, rather than accusing the OP of neglect, she needs to be looking for appropriate support to help her out at times when her illness is such that she is unable to care for her dc adequately.
OP can you speak to your GP to put you in touch with some support? As I said up-thread, you may be entitled to PIP if your disabilities/illnesses are such that they leave you incapacitated at times. At the very least you should think of claiming for the lifestyle component of pip (they used to call it the care component,)
If you have previously been very independent then it’s understandable that it’s very difficult to accept a reduction in those independence skills. Been there, done that. My illness is also such that sometimes I think I will pass out, in fact the other day I was cooking and ended up completely breathless and someone had to finish off cooking the dinner or it would have been late. It’s very difficult for me to accept this but I’ve had to. My situation is slightly different in that my DC is sixteen so is to all intents and purposes independent in their own right. But you have young, preschool aged children who are not yet of an age to be independent, and you also have older children who by your own admission have no friends so they have no let-up from your illness, especially when you expect them to compensate when you’re ill by not going to school and being with their peers but instead staying home to look after the younger children.
You need support here. It’s nothing to be ashamed of to admit that there are times you just cannot cope.
And for those suggesting that the husband needs to do more, it may not be possible. He may have to work if the OP’s illness is such that her working abilities are limited for instance, and we all have to live. If he’s supporting a household then it’s not a given that he can just take time off whenever he has to. Most employers simply aren’t that flexible, the fact that single parents and indeed women find it so difficult to work when they have small children is testament to that fact.
OP, please speak to your GP as a starting point. And look up support services with regard to your illness. There likely will be some. And engage with your DC and the school to establish what the issue is with regard to why they have no friends. Is it that they have no friends? Or could it be that they don’t want to bring people back if your illness means they are essentially carers? They need support as well, this isn’t just about you.