Over the last couple weeks, I've been getting horrible pain in my mid-back. It starts around 5:00am, and keeps me from falling back to sleep. During the day, I'm fine.
I've tried a number of different things, but last night I tested a theory that my ribs were pushing my thoracic vertebrae and causing discomfort (A in figure). So I used an extra pillow to put my shoulder on to keep my ribs slightly elevated (B in figure).
I woke up with no pain at all! I'll try it again tonight.