Lower back pain............?

I'm a 15 year old girl. I have been having extremely uncomfortable back pain lately. For the past 2 weeks. What might be the cause? I don't have my period yet... I read somewhere that might have something to do with it. It's uncomfortable to sit, pick things up, do anything? What can I do for relief like should I sleep a certain way? Helppp advil isint working very good and i cant take advil every day because thats not healthy.