For your bradycardia
and related symptoms, it is better to visit a cardiologist. You will be asked to undergo a Holter ECG monitoring for 24 hours.
Obviously you are worried about the heart diseases because it is running in your family. 2 D echocardiogram
will reveal any such heart defects, although you may not be having one.
Calcium and magnesium
tests are not really required on a routine basis at your age.
Dizzy spells are because of bradycardia. Better to avoid driving till you are tested.