The more dehydrated you are, the less effective oral anti-nausea/emetics will be. Call your doc, get some hydration and you'll feel so much better. I've had HG 4 times, the first time I was 18 and they basically blew me off back then. I was 98 lbs at 5 months pregnant. My second I was able to get my hands on zofran and I just barely hung in there. It was still super miserable though. With my 3rd and 4th (current) baby, I deteriorated much faster and was put on a zofran pump and had a nursing service to bring IVs to me. The constant dose of zofran in my system coupled with extra hydration made it survivable and I was actually able to function normally after getting stable.
It's really important that you call and get help though. Don't try to tough your way through it. Nobody is going to think badly of you for calling. <hug>