The best thing you can do is to get a handle on your past: read about trauma (The Body Keeps the Score, by Bessel Van Der Kolk), and try to connect with a trauma therapist.
Trauma often manifests itself in physical symptoms. There are paths that lead to healing...
There is hope, there are people who will understand, and you deserve it.
stopped trying to cope years ago, on my way out
For what it's worth, I haven't found anything yet. It seems that the be-convinced-in-ones-own-mind problem requires focused consideration by definition.
Just saying.
For my own part, I have this visceral unease that I don't think will go away until I have absolute (end-to-end, closed-loop) confidence in Something.
There was a girl, Lana, 16 years old. She fought, all the way...
It's horrific, and sobering, and may help you to get a perspective on your troubles.