I've been having sharp, bloating pains on my left side?

Usually, on my left side, just above my pelvis. You know, right where you appendix is? Except on my left side. When I have these pains, every time I walk, it hurts so bad. When I slouch, the pain is UN-BEARABLE. When I sit up, it feels like it's RIPPING. I can't sit comfortably at all, in order for it to feel better, it has to be gone. What could be wrong with me?