I went through this years ago and really, there was nothing truly wrong with me. It really was an anxiety reaction even though I wasn't really in touch with how much anxiety I was actually experiencing. The irregular heartbeat is distracting and feels like something is really wrong, but they usually aren't dangerous and will eventually resolve themselves, but the anxiety and focus on them ironically seems to just prolong them so it's a vicious cycle. Are you in therapy to explore the probable underlying anxiety that is creating these symptoms for you?