Chest Heaviness and Left arm pain

Dear Dr.
I am a 34 year old man having heaviness & tightness in my left chest towards the left arm. It actually started about a 10 years back not regularly but occassionally when I am too tensed. But from the last 2 years it occurs very frequently and even daily the whole working hours. One thing I have noticed is that it comes whenever I have too pressure in my work or when I am tensed. I do not have problem in my breathing, I do not have problem in doing exercises, walking or even sometimes running. I had undergone ECG check ups and the doctors had said everything is normal. But when the heaviness comes I feel like that my left hand side of chest and arm is going to get paralised or similar to that effect I am getting. It may remains for long hours and sometimes I feel too sleepy. I am worried that if it is related to any hear desease. Please do advice