Doc told me if the pain is on both sides it's not the sciatic nerve, sent me to a physical therapist, who verified that it wasn't, and gave me some excercises to do to strengthen core muscles.
The one that helped me most was laying flat on my back and pressing the small of my back to the floor - you have to isolate the specific muscles and not use the muscles in your buttocks.
The healing was slow (it's inflamation) so I bought a $300 inversion table from COSTCO. It's a traction device and stretching things apart gets blood and fluids flowing that promote healing. I got instant relief from the first time I used it - after only four minutes. Money well spent, it's healthy to hang like a bat and is a preventive measure to keep the problem from returning. Gotta walk an hour a day also. Therapist said two things; "use it or lose it" and "motion is the lotion".
Pic from COSTCO web site:
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Edit: in my case, I had zero pain when sitting or laying down - only when standing and walking.