It is not common but it is not unusual either. This site has many excellent articles written by spinal specialists. You can read about the extra vertebra here:

http://www.spine-health.com/conditions/pain/spinal-abnormalities-rarely-...

Since you are still growing and are involved with sports, I hope you are seeing a fellowship=trained spinal specialist. This can be an orthopedic SPINAL surgeon (not any old ortho) or a neurosurgeon who has additional training in the spine and devotes his/her practice to issues of the spine and back.

The best opportunity to deal with a problem, IF surgery is required, is the FIRST time around. You don't want to end up wishing you'd gone to a more experienced surgeon. These specialists will try conservative treatments first and will not suggest you jump into a surgery. You will be able to get an accurate diagnosis without wasting a lot of time.

A chiropractor has a place in the medical profession, but you need to know what is wrong with your spine before you agree to any treatment. In some cases, it can do more harm than good. I would be particularly careful since you are still growing.

As a matter of fact, if you live in or near a big city or a university teaching hospital, you might want to look for a pediatric, sports medicine guy who is also a spinal specialist! If your problem is not complex, this would not be necessary.

Good luck to you. Let us know what you find out.