Yes, revmother, I understood this to be so.
Has your doctor ruled out lumbar spinal stenosis? This is another syndrome where sitting would give relief by opening the spinal cavity, and standing would put pressure on the spinal cord causing pain.
Also common in this situation is facet syndrome, where pain is coming from arthritic facet joints.
I had severe crippling back pain Prior to my ankle surgery. When I had to remain in a wheelchair and curtail standing and bending the pain ceased. this is why we are trying to figure out the cause of the pain because the wheelchair and reclined seating temporarily cured it.
Hard to say what this is without an examination, but it could be muscle pain.
You've been in the chair for weeks and haven't used your back muscles at all. You may need some physical therapy to get yourself back in shape. Ask your doc.
best wishes.