What could cause a sudden sharp back pain?

I have never had back pain except when I had shingles but the other day i got a crippling pain in my back. I felt like I was going to cry I had to hunch over and could barely get ready for work. It started to feel better when I was on my way to work and then when i got in it was basically gone. What could cause this? (im 19 and have not had any back injury)