I am 24 with lower back pain as well. I have gone to the chiropractor since I was 16. The most common cause (my doctor tells me) is because of simple gravity. It pushes your vertebrae down and there are nerves in between that get pinched and cause it to ache. If you can go to the chiropractor, they will more than likely adjust your spine to take some pressure off and the next day, you will feel as good as new :) hope this helps
There can be many causes. Get a diagnosis first, then look into chiropractic, herbal, or my favorite, acupuncture. I was on my high school gymnastic team. I have had back, knee, hip, ankle, and who knows what else damage. I have rolled my ankles over 172 times. Acupuncture is the best for pain.