What Could Breast Pain With Swelling Suggest?

I have an occasional sharp pain under my left breast under the rib cage. Sometimes this area also swells like something is going to pop out of by ribs. Laying down and breathing helps it go away, then the next day it hurts due to being stretched. It then will not return for a few weeks sometimes months. I have been told by my doctor it is my bowel, but nothing was done to check it out (at the time of her saying that i had hemeriods but have not had those for over a year)