That is such a difficult place to find yourself; you have my complete sympathy.
First, I'd try to find a mental health professional who also has expertise with career counseling in your field.[0] That person can help you put together a realistic plan based on your capabilities, limitations, and the realities of the job market - they've solved this problem many times, so they'll know about possibilities that you don't, and they'll help you anticipate what will work well for you in the long term.
Everyone has real limitations and IMHO the great majority of people are doing the best they can with what they have. The other people might not talk about their problems and often don't even face them, so you are ahead of the game by taking this step. You just have a mismatch between your job and your current capabilities; it's easy to figure out that you shouldn't be a concert pianist, but some other things are much tougher - especially things we all are conditioned not to face, such as mental health. You only need to find what fits your capabilities and you'll be happy doing. Imagine what a relief it will be not to struggle against the tide every day.
As far as immediate income, I'd find something that induces as little stress as possible, based on what you know, while you make a long-term plan for what works for you. Don't worry if it's a great career move; take care of yourself for now.
And do your best to put your support system to work. You may be surprised how well people who love you respond.
One more thing: The bias against mental health problems is ignorant bullshit. Their insightful analysis is, 'I can't see it, so it must not exist'. Don't be stupid like they are (ignore them and maybe they won't exist). Be realistic about your problem, accept yourself, and I hope you have some compassion for yourself - it sucks, and you didn't ask for it. The fact that you put off dealing with it is natural; we're all conditioned to expect we'll fit a one-size-fits-all career and to think that mental health problems should just be ignored (that same reasoning: if you ignore it then somehow it won't exist). Now's a great chance to point the rest of your life in a healthy direction.
The best time to plant a tree is 20 years ago; the second best time is now.
[0] Most mental health professionals have experience only with careers in their own profession and lack expertise in career counseling. I'd look for someone with both skills. My first approach would be recommendations from businesses on who they send employees to; likely those mental health pros will grasp the business and career side of it. If asking your employer isn't a good option, I'd bet the HR at almost any business would give you a name; maybe contact the HR at some top companies like Google, tell them your situation, and ask if they can recommend someone. It's simple for them and most people would be happy to help someone.