Is what I'm doing at my job helping or hurting my back?

I had a similar problem. It could be the fact that you are on your feet so much. I tried doing stretching exercises in the mornings when I woke up. Not exercises - stretching mostly. But stretching exercises is the term. Things that stretch out the back muscles. Just about 10 minutes worth each morning. And that worked. It took a month to realize the benefits, but it did indeed work. And the back fatigue and discomfort went away