I Have Ms And Through Trial After Trial With My

I have ms and through trial after trial with my doctors advise have tried numerous medictions to combat fatigue. I determined that nuvigil was the medication that has helped me the most. It now seems that it is not approved for the treatment of fatigue in ms and my humana enhanced insurance will not approve it. What canI do to rectify this? I have had ms since 1984.
Thanks,
K. Myers