For years I used to suffer from back pain. Just too many hours sitting in front of a keyboard.
I tried a few things. Not pills, because I avoid those like the plague. But I went to a chiropractor, I tried scheduling times during the day when I would get up and do some walking around and stretching, and I even tried setting up my computer so I could work standing up.
There was nothing wrong with any of those approaches, but the solution that really worked for me was to throw away my regular chair and use a kneeling chair instead. Not every office supply store carries them, but some do. Failing that, you can find one online.
To go a step further, watch the video below. It contains some interesting information and some tips on strengthening your lower back.