Feel Sharp Pain On The Lower Left Side Next To The Heart Below The Ribcage. What Could Cause The Pain?

I feel asharp pain on the lower left side next to the heart below the ribcage .The pain is very intense when i do any physical activity especially walking and climbing up stairs.The pain is sometimes also there when i get excited like an adrenalin rush.I have had a heart condition( dialated cardiomayopathy) for the past five years and an year ago i suffered severe pulmonary embolysim.My body also retains alot of water making it hard to sleep and breath and i have to go to hospital to have it drained through a series of lasix intreveinous injections . I feel a sharp pain on the left side below the rib cage close to the heart mostly when i do any physical activity especially climbing up the stairs.what could cause the pain? What could cause the pain because it is very severe?