Backs are a pain. I fell on ice in march and hit low back on concrete corner of step. Lots of pain and sciatic pain with numbness. Spent 4 months on my stomach for work and 6 months with several specialists to figure it out. Recommendations from Nothing is wrong to You need a three vertebrae fusion. Problem was no obvious structural damage to vertebrae or discs to explain symptoms. Finally got hooked up with GATC physical therapy. I had muscle knots from my knees to mid back. The real culprit was the hip flexers (Sosa) as they attach at top and front of thigh and go through pelvis onto L2-3-4. The muscles were so knotted they could not relax and were compressing and twisting my spine and interfering with nerve roots mimicking disc impingement. Sitting made it worse and no amount of stretching helped. We dry needled it for 4 weeks chasing knots. Now back to 100% plus with no surgery.

Not sure of your problem but I heard the same guesses. My pt guy really knew muscle structure and function. We ruled out structural issues through multiple MRI's while searching for answers. Not saying you have same issue, but thinking about it differently made a difference and no doctor could figure it out.

Hope me you can figure it out.