Really painful stabbing sensations in my lower left back?

Okaay, so for a little while now I've been suffering from sharp stabbing pains in my lower left back and it's only getting worse. It's often just a constant stabbing, but sometimes it suddenly gets worse and makes me feel sick, double over, cry or even scream. It hurts to sit in certain positions or to even breathe in! I've asked my parents to take me to the doctors but they won't, and I'm weary to go alone. If anyone can explain why this may be, or relate it to anything that'd be great; but any help is much appreciated! Thankyou!