Knife stabbing pain in side...?

[TrueChicagoer]

I have these pains right above my hip bone on the left side, and left side only. It feels like a knife stabbing-ish kind of pain. I've been getting it pretty often recently. Surely it can't be lactic acid since I haven't been running a lot. I've actually been sleeping a lot more than usually, which is mostly because it is Summer I guess... I'm 13, I don't do drugs or drink. What could this be?