So I finally broke down and went to see the school doctor today because my back is still hurting.
He says it looks like just a really bad muscle pull (yay, no nerve damage) and recommended I increase my ibuprofen use, then gave me a giant box of muscle relaxants. If that doesn't work, then it's physical therapy.
Also, he recommended I stop gardening through the pain, because apparently that is not such a brilliant idea. Silly doctor.