Hi,
Welcome to the ehealthforum and I am really glad to help you out. Hearing one's heartbeat is called palpitations.Causes include anemia,hyperthyroidism, abnormal levels of electrolytes like potassium, magnesium, and calcium,caffeine,tobacco and alcohol intake,stress,heart conditions like narrowing of the coronary arteries, paroxysmal supraventricular tachycardias or Wolfe-Parkinson-White syndrome and medicines like asthma and thyroid medicines.
I feel that a clinical evaluation and investigations like ECG,stress echo,Hb levels,thyroid profile and blood tests measuring the levels of electrolytes are needed in confirming a diagnosis.Please consult a physician/cardiologist for the same.
I sincerely hope that helps. Take care.