My DS is 4.5 months old. He can roll from his back to his tummy, but not the other way around. He is rolling onto his tummy to sleep. So what do I do when my doc keeps asking if I am putting him on his back to sleep? I am using a positioner and putting him on his side, which is his preferred way to sleep. But he rolls onto his tummy and gets himself comfy. Do I move him back? Do I leave him?