Uh. . .why all this stress on sleeping on your back? Sounds like it's doing you more harm than good.
At this point I'm not sure. In the past, though, I've definitely felt better after sleeping straight on my back and worse after sleeping on my side.
Biology likes to shake things up every once in awhile. It doesn't help to stick to something too rigidly. Then it can all fall apart because the little bits get up and revolt at the homeostasis from boredom.