Sometimes out of nowhere I feel my heart, instead of going baBUMPbaBUMPbaBUMP, go THUMP....... THUMP..... THUMP. Its like it beats harder slower, but only for a couple of beats. I feel it in my chest and throat. I don't want to go to the doctor because, it doesn't happen that often, so if I go there, and nothing happens, its kinda like I'm making it up... Does anyone know whats going on? Has this happened to anyone else?