I was in a mva & what are long term effects of chronic back and neck pain? Is there a post diagnosis for this issue? 15 years later what can I expect?

This depends on the . Severity & reasons for your symptoms in terms of diagnosis & how in shape you are in terms of not smoking, being overweight and exercising regularly. For some with whiplash diagnosis, there can be an increase in rate of disc degeneration over time faster than what would normally occur. For most, there is no significant long term issues.
Terrific question. We continue to learn about the effect of mva's and other types of trauma. Chronic neck pain with normal mri's often get diagnosed as TMJ or thoracic outlet syndromes, if one looks closely. Chronic low back pain may be truly a sacro-iliac problem. Suggest you get pro-active, and seek out an innovative rehab doc who will investigate the underlying problems, as these could be reversed.