There are so many varieties of back pain, so this might not help, but...when my back hurts it is usually about hip level on the right side, which has been diagnosed as a sacroiliac problem. I've had the problem for many years, but it got worse when I started doing lots of cycling. The thing that helped most was to start a regular stretching routine that I do several times per week at a minimum. Stretching the hamstrings was most important for my back, although it's best to stretch all the major muscle groups rather than just focus on one thing.

This book has a lot of good stretches:

http://www.amazon.com/Stretching-20t...9313777&sr=1-1

A good physical therapist should be able to give you specific advice on stretches that should help your back.