My physiatrist who addresses joint pain and such, suggested to me for the same problem, a Roho Seat cushion. But I looked it up and they are $400. But in the meantime, I got on Amazon, A COMFORTANZA Seat cushion. The first one I ordered was “soft” But I sunk right down to the hard chair. So I ordered another one that was “firm” And this does better. But still I can’t sit for more than 45 minutes at a time and then I am back on the couch lying down but that sometimes bothers them. I wonder if it is actually the flesh that is in front of the sit bones that is hurting. Maybe eventually I will buy the ROHO Seat cushion, it is like bulbs of air, after looking at them there is one that is made from plastic, and apparently that one is not very good. But the one made with the rubber or silicone type material is more expensive but after reading all the reviews it is much better. But to pay $400 for something I cannot even try out is kind of scary. But the reviews say that when you talk to a person, they can really help you. Some people use these for their wheelchairs so I figure they must be pretty good. When I sleep at night I try to sleep on one side and then the other so that I am not sleeping on my back because I think sleeping on my back irritates the sit bones also. I feel your pain, and I just said a prayer for you.