Advice anyone? Stabbing pain under left rib cage

I was banded on 5-21-07. I have been lucky enough thus far to not have experienced the "gas pains" everyone has refered to. Since yesterday morning, I have had a stabbing pain under my left rib cage. It's awful. It hurts to breathe. When I take a deep breath, the pain shoots all over and I also have a dull achy sensation in my back. Does anyone know what this could be? Is this gas pain? Would it show up almost 4 weeks post-op with no prior symptoms? Any advice would be greatly appreciated. Thanks.