Wish I had some advice but I think you've probably heard it all. My mother was that sick with me while she was pregnant up until the 9th month and constantly in the hospital for dehydration. Unfortunately nothing worked and it was just something she had to live with until I was born. On the bright side this is temporary (I know that doesn't really make you feel any better).

Try eating small meals rather then big ones
I used to get far more sick if i went long without eating at least something
Before you even step out of bed eat a saltine cracker
Take your prenatal vitamins in the afternoon or at night
Gingerale or ginger tea can help ease nausea
Theres these things called Preggie Pops that my friend swore by

Is there a different brand of medication you could try that may work for your body

Sorry your going through this and hopefully it goes away soon!

I feel your pain, I've been that sick throughout my entire pregnancy, and yep became a frequent at the ER. I actually got hospitalized for 5 days when i was about 26 weeks, for being so dehydrated and losing so much weight. They gave me Zofran too, but it doesn't do anything I'm now 33 weeks and still fighting the nausea. Somethings I've tried that help sometimes is sleeping while sitting up (I know it sounds funny but for whatever reason it just holds stuff down easier), Not eating anything sugary after about 3 in the afternoon, drinking room temperature water, (cold water irretates the stomach) and my best advice is not to stress about it, it really does make it worse if you feel like you have to throw up, just do it, don't fight it, cause it makes it that much worse. Try to stay positive and remember it's for a good cause in the end. Good LUCK!