Up in the top of your abdomen is a section of your colon called the transverse colon, Orangeman. It runs right under the diaphragm, which is along the bottom of your rib cage. It's the next-to-the-last section of your colon, which seems strange that it's up high there, but it takes a turn and heads downward again before its contents make their exit out of your body. Gas gets trapped in the transverse colon very frequently, especially in the top left corner, which is really called the "splenic flexure" in anatomic talk. There's a little pocket in which you can get gas bubbles and air pockets and feel them up under your ribs. So that's why you might feel pains there from gas and not necessarily feel it like gas that's moving through to be expelled.