What Causes Discomfort In Upper Abdomen?

For the last several weeks I have been having discomfort off and on discomfort in my abdomen. Around Christmas I began have localized discomfort in the upper left part of my abdomen, just under my ribcage. IT is brought on by eating, and relieved by BM. My BMs vary in consistency, I may go a day without a significant BM and then go 2 or 3 times the next day. I am 32, weigh around 290lbs at 5'10. I would characterize my stress levels at normal to moderate.