i'm 17, not pregnant. but a couple of days ago my lower left back started hurting. it doesn't happen non stop, but it hurts when i walk, especially up and down stairs. but sometimes it doesn't hurt at all? when i sit down it doesnt hurt either, i think it hurts most when i apply pressure on my left leg. does anyone know whats wrong or what help i need? .. also i have not suffered any other symptoms. thank you very much 