I get a sharp pain in the centre of the chest, on the sternum and sometime it radiates to the left arm. I take half a tab of Sorbitrate 5 mg, place it under the tongue and after a few minutes it disappears. The pain appears particularly after meals, or when I walk or in the night if I go to the toilet for urinating. However, the pain is not always predictable, I walk a lot, and I indulge in plenty of physical activities also. What should I do?