Don't mess around with this, could be nothing but it doesn't sound like it. Go to an ER, they will run all sorts of tests and even if nothing is obvious they will admit you and you will see a cardiologist. Ten years ago I thought I was having a heart attack, I ended up in an ER where a very intense team went to work on me. After hours of diagnostics they ruled out a lot of things but admitted me for a 24 hr observation and and more tests by a cardiologist. I passed a stressed test and he said I didn't have a heart problem. It was a problem with my esophagus which sits right behind the heart. Guys are stubborn about such things and that gets worse with age but this thing got my attention.