If you have a primary care physician, I think you should be discussing this with him/her ... immediately. If you don't have one, get one.
There was a period when I exhibited all of the symptoms of cardiac problems, but ECG's and other tests disclosed no such thing. After a year visiting various specialists, it was determined I was suffering from a case of severe GURD and after taking Nexium, at high dosage, the symptoms disappeared. So, I say this because ... other things can mimmick cardiac problems. Best to get this checked out, soon. All the best.