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)?
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