I have a similar story, but not as serious as OP. A couple years ago, out of the blue, I started having almost constant unbearable back pain. Doctors I saw didn't know what it was. Eventually, one of the neurosurgeons, after I showed him an old MRI scan told me it was a cyst in the spine that was 80% of the time asymptomatic and unlikely to have caused the issue. That cyst required surgery and only 3 doctors in the world have done it before. During this time I started to go to the gym and train, and after some time, the pain went away on its own. Not sure if it was because of the better food I was eating or stronger back muscles that got rid of it. Since it's a neurological issue, some postures and chairs still cause pain, but it usually goes away quickly now.