Mid-back Pain More Condition_symptoms What Could Cause Moderate Mid-back Pain?

What could cause moderate mid-back pain? - mid-back pain more condition_symptoms

Well, I think it's more than half of the back pain, because the movement of the thorax influence how isolation and torsion:

I can do everything (sleep walking, exercise, sit ..), it hurts a little. It hurts when I do that later - in order to isolate the lateral chest. Otherwise, pain, and leads me to jam. I have to (carry heavy books around 2 days per week and I have) a slight curve. I do not have other causes.