Still hurts

During my two-week followup with the surgeon who replaced my shattered right shoulder last month, he said I could use my crutches again. (I need crutches because my right leg was amputated at the hip four months ago.)
"It'll feel strange," he said, "but you can do it."
I was skeptical but like many, I believed my doctor, who presumably has more experience with this than I do. When I got home I got the crutches, stood up from my wheelchair and got ready to take a step. 
My right arm wouldn't move. 
Smart arm. It knew that if I tried to take a step I'd fall down and, with my luck, break my left shoulder. 

"What has he been smoking?" my physical therapist said. It seems my doctor was going by the structural ability of the replaced joint and steel rods, which had knitted with the bones. He wasn't paying attention to the atrophied muscles, the damaged nerves, the traumatized tendons and ligaments. Instead of listening to him, I listened to my PT and got on the crutches and put small, then larger, amounts of weight on them. 
Two weeks later, feeling stronger, I took a small step. Bad idea. I didn't fall and the step seemed successful, but that night when I lay down to sleep my shoulder felt like it was on fire. What's worse is that now, seven days after that one step, it still feels like that and getting any real sleep has been impossible. I've tried pillows, I've tried ice.
"It feels like I fell five minutes ago!" I say to my bedroom. The best I've been able to manage is two hours or so of sleep at a time sleeping on my left side. Despite having a good mattress, after two hours my left shoulder starts hurting and I wake up. I pull myself into a sitting position until the pain subsides, wait awhile and try again to get some sleep.