there was a time when I had constant hiccups twenty four hours a day for a week straight, I could barely breathe it was that bad. Eventually, my family doctor recommended me to who is now my GI, after meds were ineffective. An appointment was made after a couple of days, I went in and he put me asleep and looked down my throat...that's when it was discovered that I had some kind of virus in there.
Another appointment was made about a week later, when I was ok and that's when they discovered Colitis.
I think it's always good to get another opinion.
Did your GI put you asleep and check your throat?