id see the doctor to rule out any other causes, anxiety plays a huge part in these buggers too, just get a check up to put your mind at rest
Lost of complicated and possible interaction in the little you have said, and too little specific to be of much help in relating.
But, I'll offer the following:
1) an EKG reports only what it "sees" while it is making a reading, a few seconds
2) an monitor that a patient wears can "watch for a day or much longer.
Did you have an feeling of "skipped beats" while on the EKG run? I don't mean while you were hooked up I mean when a recording was being made...usually a brief but recognizable period of the EKG examination. If not, the EKG results may not give any information relative to your problem.
It sounds like a check-up by a specialist is in order. I read your profile to say British Columbia (BC)...that being the case I understand you have state provided medical care (no out of pocket expenses) so why not see a specialist (cardiologist)?