The middle of your back would be around the level of the diaphragm, maybe the
lower part of the lungs, maybe the kidneys.
Pain in mid-
back can be due to anything. Probably, most often it is musculoskeletal. Bilateral back pain would be consistent with a muscle strain or maybe a nerve or disc problem. Back pain is like a headache -- so many things can cause it that you need to be examined by a doctor, in order to find out what is the problem.