The truth is, if your not disabled, then your doctor should write a note to your work saying you need to get up every 15 to 30 minutes, for about 5 or so minutes to let your back rest. I am sure you know spinal stinosis is the narrowing of one or more areas in your spine, usually causing a disc to bulge, causing pressure on your spinal cord or nerves that branch out.  This will cause tingling, numbness, or pins and needles either in your arms or legs, not to rule out, your neck, hands, and head.

PS sitting for long periods of time is very uncomfortable.  You seriously need to stand up and stretch to avoid this problem.  Since your problem is in the Lumbar spine, it involves your legs which makes it a must to stand up.  Try to remember medication is only used to help ease the pain, it is not to "fix" the problem.  You need to try to do the best you can with the "chronic pain" by "avoiding" things that irritate the problem.

Good luck

Rose