I read the whole post. I'm not sure I have any useful advice, but I can offer my largely uninformed opinion.
It seems like you held yourself up to unrealistic expectations. You are who you are, and while you can change that, it's a difficult and slow process. Not everyone can be a doctor or a lawyer and that doesn't reflect poorly on you at all. You need to crawl before you can walk, and walk before you can run.
You're in a low place right now, and the only way I would know to get out of it is to seek help. It sounds like a platitude, even to me, but without some sort of support it's easy to continue with the status quo.
I hope you find some way through this.