Cats are super tuned to their chosen human - he's probably worried about you. Do you have a small pillow you can put under your lower back? If your spine is too straight, you'll get pain in the lower back. I've stopped sleeping on mattresses or mushy things. Just a little pillow for lower back and a nice hard floor - it has helped.
It might not be caused by sleep, though. Have you had a blood test recently? And are you drinking enough water?