I sympathise, Harry. I had a disc go in my upper back, a couple of years ago and, like you, found lying down flat in bed very painful.
It drove me to the doctor seeking some form of pain relief eventually (I thought I had pulled/torn some muscles but I was also getting
referred pain in the top of my left leg above the knee). He prescribed an anti-depressant drug that has been found effective for nerve
pain too. Though the dosage was way below what a depressed person would take, the damned things knocked me out at night, sure
enough, but I found I couldn't truly wake up the next day! I was walking around in a sort of foggy state and there was no way I could drive
in that condition! I stopped taking them, of course.
I had a short course of physiotherapy to strengthen my core muscles and I was right again after about six weeks.
My mother-in-law had the intraspinal injections to treat arthritis but found them ineffective and the specialist doesn't propose trying them
again.
Sorry I can't offer any advice that would be of practical help. The words "posture", "weight" and "exercise" seem to come quite readily from the lips of
doctors treating back pain ...
Good luck and keep smiling!