Hi, I Am 26 Years Old And I Have Been

Hi, I am 26 years old and I have been having this problem a little over a year now and it started a little after I had an anxiety attack. It's behind/under my left breast it stays steady everyday and a few times it becomes more intense. It feels like inflammation, or like something is sitting on top of it or tightness sometimes and really really bad discomfort all the time. I did an EKG, an MRI and an X-Ray and they all came out normal. I also took Gas X and it did nothing. But I need an ANSWER no one seems to know anything. Please help!!