Chronic Stiff and Locked Up Lower Back

Hi everyone

I’m hoping that someone may have experienced or come across a similar problem to this before

For over 3 years I have had a stiff lower back. L2 - L5 are completly locked up and when I try to separate the segments of my spine individually, they just move as one unit.

I have had an MRI that shows no disc problems
I have seen about 10 physios, chiropractors, osteos etc who haven’t been able to tell me whats causing it and haven’t been able to fix it

Im in anterior pelvic tilt, and spend a shit load of time working on core stability and flexibility to try and fix this with minimal results as the back always pulls me back into APT

I think Quadratus Lombourum may be tight on the left side as the pain is usually worse on that side, I get sciaitic like symptoms in my left hip (but not the left quad), and when I lie down I can feel my left hip hiking up