I can still run, play tennis, etc. It helps to hang from a bar by my arms and stretch. Seems like something is compressed in there and likes to stretch. Pain is in very lower area sometimes on left and sometimes on right. Sometimes both sides.
Some infections cause back pain as well.
The fact that yours has lasted so long, comes and goes, and is improved by certain physical activities suggest a muscular origin. Despite massive numbers of patients with back pain, traditional medicine hasn't done a great job of figuring out or treating this problem. One fairly recent option in traditional medicine that seems to be working well is treatment at a back pain center. These facilities often bring together many treatment options, ranging from surgery to massage. Ask your doctor or local hospital if there's a back pain center nearby, and give them a try.