If on Short Term Disability, do I have any recourse for a settlement or severance in a right to work state?

I am on STD for a herniated disc with no preexisting condition. My occupation requires me to drive 5+ hours a day as a pharma rep and that could have contributed to the disc issue since I never had previous problems. I also have cervical spondylosis, which I know is considered disc degeneration. I am on good terms with my company and a severance may be discussed soon. I have not gotten any better and have had every type of conservative treatment over the past 3 months. I saw a surgeon who said he thought time would heal me but it hasn't. I can no longer sit for any significant time and am on oxycontin to relieve the pain. My quality of life is terrible right now and am concerned what future work I will be able to do and when.