Hi! I have carefully gone through why you have been worried so much.
There might be three possibilities with what you have described.
1) It may be a benign anxiety
induced transient cardiac arrest
/ complete heart block
, where you might need only reassurance & cognitive behavioral therapy
, exercises & yoga.
2) Smoking may cause transient dysrrhythmias, so you are required to stop smoking immediately
3) Although your EKG & cardiac evaluation is normal, you may have some intracardiac conduction defect, manifesting as transient symptoms, & so a thorough cardiac evaluation including 24 hour ambulatory cardiac monitoring would be needed & if it detects an anomalous conduction pathway causing intermittent heart blocks or dysrrhythmias, then with consultation of an eminent cardiologist the problem might be cured completely by either radiofrequency catheter ablation
of the anomalous pathway or with antiarrythmic agents or implantable cardiovertor defibrillator.