Hi there ~
I understand your concerns. Having light headedness diarrhea
with increase in heart rate
and a normal EKG with normal electrolytes are sure signs that you are having no problems with the heart but seem to have an issue with your nervous system. It is not unusual to have these symptoms an Parkinson's disease and I recommend that you get yourself tested. In the meantime if you have any serious symptoms I recommend that you go to visit with your ER doctor.
I hope this helps. Take care and have a lovely day!