What Causes Upper Right Side Pain Under Rib Cage?

I am having upper right pain under my rib cage.. it gets worse when I walk. I have had this for 3 days now with severe heartburn. Could this be a gallbladder issue? And if so, will it go away on its own? i am 36 and in good health... do not eat fatty foods. I am 5'7 and 130 lbs