OP, I not only have a lot of sympathy for you, I also rreally want to offer you some hope. I spent decades thinking of myself the way you think of yourself. Unable to hold down jobs of any sort. feeling like there was something fundamentally wrong with me and longing to be 'normal'.
I'm in my mid-fifties now and genuinely have no desire to be 'normal'. It's not that I love having ADD, but I fully accept that I have it and even appreciate certain aspects of it. My life settled down when I started working for myself. I found a niche I was very good at that paid OK, and I got some counselling on how to manage finances and more counselling on how to manage my time. Then I set out to do part time hours because I recognised I need a lot of down time to be able to function normally.
You are clearly very intelligent. You wouldn't be a teacher if you weren't. And you aren't useless at everything. You passed a degree and a PGCE or you completed a BEd, so you managed to sustain your focus enough to do this. You also get job offers, so you must have some charm and ability to convey your expertise in your subject. But you lose jobs because the day to day environment doesn't suit you.
But something will suit you. Is there any aspect of teaching that you don't find stressful? The subject research or the actual interaction with pupils?
Make a note of the bits you find least stressful and most stressful. The bits where you always come unstuck and the bits you manage to muddle through. Analyse the two lists. You need to avoid the stuff that you always fail at and develop the areas that you find easier. So, if you tend to fall out with parents, then interpersonal skills aren't your strong point. If your planning always drops off half way through the term then you need a job where being super organised is not a priority, or where there is not a mountain of supplementary paperwork.
But there will be aspects of your training and experience that you undervalue because they do come naturally. It's a matter of discovering them, valuing them and building a career around them that can keep you solvent. It isn't easy but it will be better than before.
You also sound like you need more support in your life. At very least refer yourself for NHS free 6 sessions of counselling and go to your GP to ask for ASD, ADHD tests etc then look for adult support groups in your area.