Normal pulse rate is 60-100 beats per minutes. A pulse rate of below 60 is called bradycardia. There are many causes of this problem. Sometimes, it can be normal especially in well developed athletes. In some individuals low pulse rate and low blood pressure is genetically inherited and does not cause harm. In majority of people, this problem can be due to some other problems like heart diseases which you excluded, aging, electrolyte imbalance and hypothyroidism. So, you should discuss these points with your doctor.