Left Back Pain More Condition_symptoms What Would Cause Pain In The Mid Left Hand Side Of My Back. Not Continuous But Hurts More When I Breath Deep?

What would cause pain in the mid left hand side of my back. Not continuous but hurts more when I breath deep? - left back pain more condition_symptoms

I'm on a strict low-fat diet low in carbohydrates and weight train 5 times a week. It feels like a muscle strain or tension. In fact, the pain came in my day off. I think the kidneys are lower, but not sure.