Are arrythmias not a concern if they occur on and off? my dr thinks i have some type of arrhythmia which is hard to catch on the monitors.

Usually no: If your echocardiogram and EKG are normal, at your age, the risk of a serious arrhythmia is 1% or less. The only other reason to try to catch it is if the symptoms are very bothersome. The next step would be to get a LINQ "injectable" monitor that lasts 3 years if it needs to be investigated further and if wearable monitors have been unrevealing