right back pain only when deep breathing

I started 3 weeks ago with a back pain that only occurred when taking a deep breath.  I waited a week to see if it would go away and it didn't. I went to my general practitioner and they prescribed an anti-inflamatory stating they think I strained a back muscle.  I argued that I had not done anyting and that the pain only happens when I take a deep breath.  Another week later with no relief I went to my chiropractor.  After examination and readjustment, I went back a week later with no difference.  After presssing on my lower spine there was tenderness on the spine, as he tried to stretch the area in question I had a slight burning sensation on the spine.  He has ordered an MRI for me on this coming Tuesday.  I am miffed.  I have been an athelete my entire life and I know what a pulled or strained muscle feels like, and the muscle does not hurt and neither do my ribs at all.  Only when deep breathing. Now it seems to be moving around to the right side of my body but still under the rib cage.  Anyone have this or know what this could be.