Heart beat related problem. To feel it?

Sir/madam, i am a patient of hypertension since last 2 years, when diagnosed bp was 144/90. Doctor prescribed me Nebistar SA , now my average bp is128/80.and now i am taking the same medicine alternative day as prescribed by my doctor. From last few days it seems i can feel the sound of my heart beat , only in lying down in left side position. But there is nothing when i am sitting in chair or standing or walking,but in supine position very low or nothing. No other abnormality. I can't remember whether i felt this heart beat before or not.Pulse rate is 82 bpm. I am a obese person with body wt 75kg and height 5ft 8inch. Is it normal to feel it ? Or any serious problem. Since i am in a village out of my town, no good dr nearby. Please suggest me or this is side effect of the drug(Nebistar SA) ,or a health problem.