I was just dxed w/ pericardial effusion. i'm still experiencing many symptoms (short of breath and low bp) but my doc says he will treat it. why?

You mean how: If the pericardial Effusion is the likely cause of your symptoms you should be calling your doctor now or go the ER as the situation requires urgent attention that will need removal of the fluid usually by needle aspiration. Otherwise if the pericardial fluid has no direct bearing or your symptoms, anti inflammatory drugs are prescribed. Either way it must be resolved now than later. Call MD