How come my back only hurts sometimes? And when it does hurt I feel like its in my spine. And I just curl up in a ball and cry.

See your doctor. There are many potential causes for your back pain, including damage or strain to your muscles, ligaments, facet joints, vertebral compression, or pinched nerves due to spinal stenosis (narrowing) or disc herniation. It could even be due to a tumor. Kidney stones are usually felt in one side of the back, not in the spine, but often hurts only sometimes, and this type of pain is called renal colic.