I've been having a sharp pain run through my back, it's really uncomfortable...?

[?Ello ? Vee ? E?]

Say i'm laying on my stomach and I have my head propped up on a pillow, underneath my chin then I move to get up... I get this sharp pain in my back/side. Sometimes I will be sitting indian style on my bed and it hurts SOOO bad. I literally scream out loud because it hurts so bad. As fast as the pain comes, the pain leaves. I stretch my back throughout the day, and it helps for a little while.
I also have to sleep with a body pillow so that I can sleep with it between my legs... If not, my back will hurt. But, that's only when i'm on my side.

Could it be that i'm twisting my body in a way that my back/side doesn't agree with? Or could it be something else?