Hun, you don't just have nausea and vomiting. From the sounds of it, you have Hyperemesis Gravidarum. And yes, a lot of times zofran 2x/day doesn't quite cut it. HG can be life-threatening to both mother and baby so it's critical that you get the medical support that you need.
Please do some reading on www.helpher.org. There is also a forum there of women who are going through the same thing and women who have been through what you are going through. It's a valuable source for support and information. They are part of the reason that I can say that I am an HG survivor.
I've been there. Please get the help that you need. If the zofran pills aren't working, look into getting the zofran pump. That delivers a steady stream of the medicine so you don't go through the ups and downs as it wears off periodically throughout the day. It sounds like that might be a problem right now for you.
For me, my protocol looked like this: Zofran pump with 24 hr subcutaneous drip, benadryl, meclazine, occaisional fluids.
You are not alone. You can make it through this. You just need support of your doctors and other women who have BTDT.
(((hugs)))
Edit to add: Yes, the Unisom in combination with B6 has been helpful to many women as a part of their protocol. I will be using that in my "next time" protocol.