Welcome, Smiler! Glad you found us.
First things first. There are a zillion things (almost!) that can cause back pain. Here’s a nice overview article on things to consider as you approach a diagnosis:
http://www.spine-health.com/topics/cd/hurt/h01.html
You are considered young among most of your peers here, so I am curious, what brought on the pain? Is your pain diffuse, or distributed throughout your entire back? Any other unusual sensations? Did have any accidents? What kind of doctors have you visited?
One causal factor that is often overlooked is pathogen-based inflammatory conditions. Examples of this include fibromyalgia, Lyme et al, caused by mycobacteria. Some people in this community have these conditions. But you don’t see much about this complex issue, even on prominent sites – but I predict you will see more in the coming years as people “connect the dots.” (These conditions also can complicate bone growth, I'll address this soon in another post.)
I look forward to learning more, I hope we can provide the support you need. If nothing else, framing the questions for your medical providers may help...