I Constantly Experience Heart Palpitations And Have Seen A Cardiologist

I constantly experience heart palpitations and have seen a cardiologist on a few occasions. Just in the last few days it has started to flutter and make me cough.....like it catches in my throat. Normally when I experience palpitations its if I have not had enough sleep, over indulged in caffeine or run down. I do feel a bit stressed out lately but I can't think of why this could be happening. It seems worse when I lay down or sit. If I push in between my rib cage I can make it start up fluttering and beating funny. What do you think?