Hi, I Have Been Having Pain On The Upper Left

Hi, I have been having pain on the upper left side next to my left breast but about 6 inches under my armpit. It's been going on for almost 2 weeks now, and it's a dull pain that is gnawing at me with spurts of great pain at almost feels like a burning sensation. Today is the first day that I am noticed that my stools have been darker than usual and have an almost gooey or sticky looking texture