Hi, Its Been One Year, Randomly I Feel A Very

Hi, its been one year, randomly i feel a very less sensation on above the left chest when ever i take stress. Last year i met with a doctor and my chest X-ray & ECG went normal. He said its bcoz of weakness. I joined gym than after and never felt back, but when i left d gym and handle lots of pressure, so again am feeling the continuous feel on left side.
regards:
MS