Tightness in upper abdomen upon inhalation
 

Hi, for the last week or so I have had tightness in my upper abdomen, just below my rib cage and sternum, which makes it difficult for me to take a deep breath.

It is always much worse when I first wake up in the morning and gets better as the day goes on, however it always there.

A little background about me
I'm a 21 year old male, 170cm, 59kgs. I exercise every day (swim) and am otherwise healthy.

I do not have asthma (was already tested for it)
I have had a chest xray which was all normal and I don't have any coughs or sputum.

I am just stumped as to what it could be.

If anyone has any ideas or suggestions please post them

Thank you