Do you have a deskbound job?
If the answer is yes then the chances are that your posture is being compromised bringing as a result niggling pain not only on your lower back but also on your neck and shoulders (see joint pain & injury management). Unless there is a structural condition (a condition from birth) with your spine such as kyphosis, lordosis or scoliosis, bad posture is generally the result of weak muscles around your core (see Core Stability) back and possibly gluts. Daily activities can also be blamed for back conditions such as ballerinas developing a lordotic curve, dentists suffering from scoliosis just like desk bound jobs leading to a kyphotic curve.
In all the years I've been working as a personal trainer I've encountered several postural issues in almost all my clients. These issues become the main focus of my training sessions when designing an exercise program. My objective is to reach the client's goals with the right exercises.