Sorry @Lostcause999 I have only read your posts so far, so this has probably already been suggested, but you sound very depressed to me. I look at all the experiences you have had, including getting a degree in English literature, and having been a teacher, and even after a reasonable gap in teaching you were still wanted back!
Then on top of all of that you have been a single stay at home Mum, so not only do you have first hand 24/7 hours experience with very young children, but also you have had plenty of experience at budgeting and planning, and making purchasing choices... I can't even begin to list here all of the relevant life experiences you have had for a wide range of careers, but if you can't find your confidence on your own, many job types have short refresher courses at colleges and on work placements.
So, I come back to my original thoughts, you do seem to me to be quite badly, but also understandably, depressed. As you haven't mentioned your DCs father/s at all, I presume that you haven't even had someone else who you can trust implicitly to only have your DCs best interests at heart. So you may have had to make all of the major decisions about their lives and welfare all on your own - and that is on top of having to make all the day to day decisions on your own as well.
I think you need theraputic counselling, and some advice on what support there is for single parents available in your area. I hope that you (unlike me) have at least one close, sensible and intelligent friend who you can spend even an occassional evening with, having some wine (or whatever your tipple of choice is), and maybe putting the outside world to rights (if you do come up with some good ideas maybe send them to your favourite national newspaper, with copies to your MP and the Prime Minister, and the leader of your favourite Political Party!! 🫢😉), or just a good old chinwag about your favourite books, music, TV programmes etc. I don't think that we should always focus on the shit in our lives, we need times to relax, and to not always be in our most serious and responsible adult modes.
So if you think that there is any chance that you may be depressed then please try hard to get a double, face to face appointment with your GP, and tell them that even if the mental health care in your area is self referral, you just don't feel like you have the emotional energy to do all of that on your own at the moment. If you are offered any antidepressants to help tide you over this particularly difficult period in your life, along side some counselling, and/or some group talking therapies, then please give taking them some serious consideration - they can make such a difference if taken under expert supervision.
I do hope that on this occassion I am completely wrong, and that you don't feel down or depressed at all, and if that is so, I am sure that you have already had lots of Mumsnetters telling you that you are of course young enough to start your career life again from scratch, if that is what you want. If they have, please believe them. I hope you are feeling much more positive soon OP, your adult life so far has shown that you have managed brilliantly, and I know that you can and will, continue to build on that 🩷🌻x