I am a 35 yr old male, For the past few months on and off, I get random thumping feelings in my chest, like a harder heartbeat in middle below sternum without pain. Now sometimes it is followed by a burp, but not always. I do notice that I have alot of gas (burping) regularly. Anyway, when I feel my pulse when these "thumping feelings are going on, i can feel it. Its almost as if the beats stop for a split second, then there is one, two or three strong one before going back to normal.  What can this be? Can gas affect my heartbeats, or am I just feeling gas and thinking its my heartbeats? Can it be something entirely different? Again I have no other symptoms, I train alot of cardio and never have any problems. If it was something serious, wouldnt I have a hard time doing cardio? I appreciate all your feedback. Thank you.