I Keep Feeling The Mild Pain In My Chest And

I keep feeling the mild pain in my chest and left arm whether I smoke or not and vanishes after sometime.
Few month's back , I was in office and suddenly felt chest discomfort accompanied by left arm pain ,nausea,cold flashes and felt like loosing control over myself.
I was rushed to hospital , where I was observed for a day .ECG ,ECHO & STRESS ECHO was normal . Also cardiac enzyme test was negative . Since then the symptoms have occured twice and ECG was normal everytime.