Hi Lainy,
I read a story about a cancer survivor in the Livestrong book by the Lance Armstrong Foundation who had the same problem with severe hiccups that lasted for months at a time. The story said that the only thing that finally stopped the hiccups was an anti-psychotic drug and it somehow had an effect on the same thing that was triggering the hiccups. The article did mention his struggle between dealing with the nagging hiccups versus the side effects from the anti-psychotic. You might ask your doctor to research the anti-psychotics as an option? I hope this helps.
Good luck,
Kelly