As you said, "it's been over a year that eh pain has only gotten worse."
Now it's time to stop the thought process of "I'm too young for this" and swallowing supplements and yourself to a doctor to find out what is really going on.
It really isn't as uncommon as you think for teens and early 20's to have spinal problems.
Spinal problems can come from a genetic component as well as many other things, but at this point the why is not relevant, the diagnosis is.
So here is what you need to do.
You need to so a top rate spinal surgeon to get a proper diagnosis and see what is suggested.
If I where you, I would seek the opinion of a sports medicine orthopedic surgeon who specializes in spines.
the reason I say sports medicine is that you are very young, and sports medicine spinal surgeons are the most conservative of all types of spinal surgeons and they will only do surgery if there is no other alternative and they always start with the very smallest incision needed and enlarge it if they have to.
You will need a new MRI as well, and maybe some other tests, depending on what the MRI shows and what the spine surgeon says.
The accuracy of an MRI is only good for a few months and things can change very, very quickly.
The fact that you are getting worse is not a good sign, you need to see a spine specialist as soon as possible to determine exactly what is going on and what to do.
4 years like this and getting worse, is 4 years to long.
Get yourself moving and get a spinal surgeon, a sports medicine orthopedic surgeon who specializes in spines and find out what is going on.
And don't be afraid of the name spinal surgeon. A good spinal surgeon will always go with conservative treatments before even thinking about surgery, unless there is strong evidence that there is serious damage going on that will result in very serious complications.
I, myself have had 2 spinal surgeries, the most recent June 2008, and I use a sports medicine orthopedic surgeon. I wouldn't use any other kind of spinal surgeon and I had quite a few other opinions with other types of spinal surgeons.
Good luck and let us know how you are doing and what the spinal surgeon says.
Fran