I wonder if it could be pancreatitis. Your pancreas is on your left side. It is on the upper side right behind your rib cage. I have an enlarged, fatty, liver with a cyst on it, and when it gets to hurting real bad it makes my pancreas act up. Your problem may not be that serious, just something you might want to consider. I hope you can figure out what is wrong, and get to feeeling better soon!