I would take him to the doctor too. Definitely, if you see a difference, there is something going on so you should have them check for infection. I had another thought, too. Is it possible that he is hearing better, so little noises at night are waking him? Or maybe he is experiencing some disorientation because of the changes to his vestibular system by not having the fluid where he was used to it being. Maybe he feels off-kilter or dizzy laying on his back at night. If the doctor says there's no infection, I'd experiment a little with sleeping position - would propping him up or putting him in a car seat make a difference? Or is he too old to swaddle? If he feels unanchored from the bed because of the changes in his inner ear, feeling the blanket around him might make him feel more settled. (can you tell I have a kid with sensory issues? ha)