I had heart rhythm problems from magnesium deficiency personally.
Excerpt from Wikipedia's article Premature ventricular contraction...
"Some possible causes of PVCs include:
Adrenaline excess;[8]
High blood calcium;[7]
Cardiomyopathy, hypertrophic or dilated;[7]
Certain medicines such as digoxin, which increases heart contraction or tricyclic antidepressants[7]
Chemical (electrolyte) problems in the blood;[11]
Contact with Carina (trachea/bronchi) when performing medical suctioning stimulates vagus nerve
Drugs such as:[7]
Alcohol;[12]
Caffeine;[13]
Cocaine
Theobromine;[14][unreliable medical source?]
Myocardial infarction;[8]
Hypercapnia (CO2 poisoning);[7]
Hypokalemia — low blood levels of potassium[a]
Hypomagnesaemia — low blood levels of magnesium[a]
Hypoxia;[7]
Ischemia;[12]
Lack of sleep/exhaustion;[16]
Magnesium and potassium deficiency;[7]
Mitral valve prolapse;[7]
Myocardial contusion;[7]
Myocarditis;[7]
Sarcoidosis;[17]
Smoking
Stress;[16]
Thyroid problems;[18]"
Your doctors have cleared you in terms of your heart's health, and in fact, you do not describe any symptoms of disability--other than the fear you experience when you feel the irregular beats.
Therefore, your real problem, the one that is making you miserable, is fear. It is time to make an appointment with a doctor who treats anxiety disorders. You can get real help if you are willing to admit that fear is what is ruining your life.