What is his current weight? What was his weight when you purchased him? I had a sand boa for a long time and had nothing but issues with him (He was a rescue long story). Try getting him on a good feeding/weighing routine, and make a notebook or something for him recording his sheds, weight, and when he eats. Also did he have a bad shed? He looks like he has old skin around his whole body, either that or he'd dehydrated.