What Causes Periodic Pain In Chest?

I am a 36 yo female. 5 4 athletic, fit body type. I have had periodic pain on the left side of my chest for 2 years. Two years ago the doctor diagnosed me with costochondritis. I was prescribed prednisone. The pain went away. The pain in the beginning was so bad it hurt to raise my hands above my head. I would describe it as a stiffness, crampy, sharp, achy deep pain. My chest has never been sore to the touch. About 8 weeks after finishing the prednisone, the same pain returned. Instead of taking prednisone again, I began eating coconut oil daily (as an anti-inflammatory) and the pain went away. Since then, the pain comes back sporadically, but is very dull. I may feel the dull pain once every several weeks, once a week, or several times a week. I usually feel the pain when I move my upper body to a new position, pick up one of my children or some other movement that involves flexing of my chest. From what I read in regard to costochondritis, the pain should be completely gone by now, and my chest would be tender to the touch, which it has never been. I have never had a test of my chest done. However, I do have an MRI scheduled on the 15th for a shoulder injury I ve had for one year...(chest has been 2 years) At the same time, they have agreed to do an MRI of my chest in case the two are related. Any other recommendations or hunches would be helpful. Thank you.