Left Rib pain with upper back pain.

It started a month back, I didn't had any injury, as far as exercise goes, I do light yoga, that's it. I did handstand too couple of times. The dull ache/discomfort is just below the breast and it goes to back and side of the body(under armpit area to chest side) Sometimes it feels like air is trapped under breast, it's not consistent, comes and goes. Sometimes it's sharp pain for few minutes from shoulder area to arm to upper back to rib lines near chest left side. I have done everything I was told by doctors from heat compression to pain killers to rest to light stretching, it doesn't go. No swelling, no bruises nothing. Sometimes the pain is in breast for few minutes and subsides. I did my ECG and Echodiagram to be safe, all normal. What is this discomfort?