The pain was kind of sharp to where it hurt more when I would breath in. No I dont have acid reflux and yes I do cough a lot. I have a night time cough due to asthma. I have had a chest x-ray done recently b/c I was in a car accident back in October and my sternum is fine I do have a rib on the bottom left still a lil out of place. I know my heart is healthy no problems there...Im 23 and in shape only 120lbs and exercise regularly. That was the first time I have had pain under my sternum. I have had a couple times where it feels like my whole chest (front and back) hurt and cramp up and its a very sharp pain when I breath in or out and I dont want to move and it will last for a few hours and then will just disappear. I usually get chest pain around my back where my ribs are...it has to be related to my asthma b/c I start to feel short of breath. Which I am feeling right now....with some wheezing which is unusally for me...with some chest tightness in the front. The longest it will last is a day.