I have similar issue but it is more evident when sitting in a soft cushion chair. This plays havoc with my sciatic nerve. I have been sitting on hard chairs which seems to be counterintuitive but it allows me to sit for much liner periods of time. Your other option is get a cushion which is attached to a battery pack which inflates and deflates periodically. This has been a life saver. The one that I have is made by Best Seat but I believe they are out of business. Google "Alternating Pressure Air Cushions" and you'll find a selection of styles.