Based on your answers, some of the most likely causes of your back pain include
sciatica
disk disease
spinal stenosis
spondylolisthesis
muscle strain or spasm.
There are other, rarer possibilities, as well.
To decrease pain, avoid overuse and try over-the-counter pain medications, a heating pad or topical treatments (such as Icy Hot or Ben Gay).
While these measures may help, it is important that you see a physician if symptoms are getting worse or not improving over time.