I have burning pain in by lower and upper back when sitting and lying mostly around where there is contact between chair/bed and my back.i have in the past sat on a chair 15 hrs each day(cause?).

Low back pain: Probably related to muscle spasm or strain from prolonged sitting. Try stretching exercises before and after work, and get up during work every 2 hours to walk around.

Be seen for an eval: Long-distance is not a good way to evaluate this sort of thing. See either a doctor, chiropractor, exercise coach or other experienced person. Backs are important.