I had the same with my first and took Restavit tablets (just 1/2 once a day) from the docs script after I'd been suffering for about 8 wks. This time i took it as soon as the sickness started (5wks, oh joy!) and bought it over the counter (no script) at the chemist (about $15 ). It's actually prescibed as a mild sedative so you'll have to say its for that as not many pharmasists know you can take it for m/s and won't issue it. It's kept things under control this time and I (touch wood) haven't thrown up (now 13 wks). I also started acupuncture at about 6/7 wks which I think probably helped too.
I feel for you though. I reckon if I had remembered more acurately how I would feel at this early stage I may have thought twice about having a second!!! Thankfully it does improve!
Good luck!