Long term severe back pain in teen?

I just turned 19 and have had severe lower back pain since I was 16. I've seen my family doctor and he prescribed muscle relaxers that no longer works & my symptoms have become worse. I don't have insurance so I'm trying to find out if anyone has had similar symptoms & if going to the hospital un- insured is worth it...

The past year the pain has gotten worse, its all over my lower back and even goes into my upper back. my legs have been weak and I even lost control once and fell. it's hard walking up hills and stairs without feeling like my legs are going to give out.
Its like a stabbing pain in my back and legs and now into my hips. It hurts the worst when sitting and when I try to stand I can't stand up straight for several minutes and walk with a limp.

That's about it, any help is greatly appreciated!