might be skipped beats - Check PVC
You have to be more specific than that. In many people, including myself, the heart stops on an outbreath and then starts again when you inhale (actually, it just slows significantly but it can feel like a beat is missing). You could also have a heart block where the conduction of electrical stimulus spit off by the upper chamber's 'spark plug' is not translated to the lower chamber every time.
Your problem, if there even is one, could range from immediately life threatening to totally benign so you should at least get an ecg.
When I have extra beats... the regular beat comes, then right after the extra beat and then a long extended time passes until the next beat which is more powerful. Maby this is what you are experiencing ... Doesn't feel nice ... huh!