My lower back pain is due to pulled muscle in the lower lumbar. Ironically, stretching it is the worse thing for me to do. In order to alleviate pressure on my lower lumbar I actually increase my stretches towards my hamstring, hips, and upper shoulders. Basically, I force my lower back to be stiff and I compensate for the lack of lower back pliability via the curvature of my hips and upper back.
Purely anecdotal and bizarre, but it is where my research led me and I haven't had back problems since. It's also increased my ability to gramby roll, but that's a different discussion.