Pressure under rib cage, affecting exhalation and speaking

Hello, I hope this is the right place to ask question, I have a symptom that so far I haven't been able to find an answer. I am actually not a native English speaker but a few years ago when I started learning I felt a strange sensation of unable to speak out words that require longer or deeper exhalation. I thought it was a matter of practice but years later I still have this physical difficulty, and I realized that this comes from under my left rib cage, it's like something is pressuring the rib cage so that it can't contract during normal exhalation, but inhalation is fine. I don't think it's a problem with my lung and I did chest x-ray and abdominal CT scan and both results came back normal. My gastroenterologist suggested the possibility of gastric mortality issue but the drugs for treating that isn't helping. I can't wrap my head around about what is wrong with my body, I can't find people with similar experience, but what I feel is very strong and it persists, not come and goes. My life quality is drastically lowered by this symptom as I have difficulty with communicating and even reading fast (constantly out of breath). Any suggestions on what the next step should be for me?