What Causes Severe Pain Under The Breast?

Hi. I have a pain under my right breast that shoots under my arm with a burning feeling. I had a upper G.I , stress tests, echo cardiogram, blood work, ultrasound, and a CT Scan and everyhting negative. They located a nodule on my thyroid and I will be seeing a gastronologist next week. I also have a little inflammation, so I am taking nexium. What did you think this burning sensation is? Thanks,