Help regarding Chest discomfort. To do.

Dr. My brother is having a mild discomfort and pain in his left chest and left side back from past 7-8 months. BMI is in normal range and age is 24 y old. Symptoms First three months: Trouble speaking, high heart rate, left side chest pain. Continuous pain and discomfort all the time. So he checked with a specialist cardiologist and all ECG, ECHO, TMT Stress test, Blood tests including sugar thyroid all reports are normal. So cardiologist told their is no problem with heart just gas and anxiety maybe causing these symptoms. Then he stopped visiting to clinic. But the pain and discomfort is still present all the time and not improving. Its been 8 months now. Type of pain : Left side chest and left side back pain (mild), pain in chest while laughing ( only sometimes), feeling of chest pressure and discomfort increases if not slept properly during night. Location of the pain is in whole chest it keeps shifting from one place to other. Please suggest what to do.