How do I get my doctor to give me pain medicine?

I've had chronic back pain for over 3 years and I am only 19. It is really severe and have tried all kinds of treatment - acupuncture, massage, chiropractic treatment, physical therapy, injections, etc. Nothing has worked. Advil does not relieve any pain, either does ultram or muscle relaxers. I suffer every day and it is really bad. I feel like I can no longer take it I just need relief. Doctors won't prescribe me any pain medicine as they are worried about addiction. I don't care I just need relief, there's nothing that's helping me and I can't take this pain. How do I convince doctors to give me a prescription for painkillers?! I can't take it anymore.