I have been sleeping exactly as you describe - with the pillow and the positioning and everything. It's not my hips/pelvis that hurt, it feels like a pulled muscle or pinched nerve in my left buttcheek going down to my left upper thigh.

I will ask about the back sleeping. I've always thought it was a no-no but if it's not, man, I'm going for it. I have always been a solid back sleeper.