Based on your answers, some of the most likely causes of your back pain include
disk disease
sciatica
spinal stenosis
spondylolisthesis
a 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.