I've said the same before... with my first HG baby... then my second. But I'm truly committed to this third being the last, lol!!!
Hang in there, I KNOW all too well how hard it is. I had HG and gestational diabetes with my first. With the second, I had HG, placenta previa, herniated (due to the constant sickness), and followed all of that up with a c-section. This time around, HG and gestational diabetes is seeming fairly likely this pregnancy. The GREAT news is, it's all finite, and you will come out of this with a fantastic reward (though it is sooo hard to bond with baby while HGing - I'm even having troubles this time around with that issue).
I'm assuming you've already switched up your meds? My present OB is discussing a change in my meds next week, and she explained sometiems one builds up a resistance to Zofran over time and a change in meds can make all the difference.
Best of luck to you and try sooo very hard to focus on the end result. You can do this!!!
3rd time HGer
HG Baby 1 born 10.31.04, in the States - treated with Reglan, which resulted in dystonic reaction, and IVs. Developed GDM, as well.
HG Baby 2 born 9.3.07 in Australia - Zofran, weekly IVs, misc other meds, no GDM.
HG Baby 3 due September 2012 - HG treated with Zofran primarily. 8lb weight loss so far.