I feel for you ds was ill all last week with sickness and diarrhoea. At one point NHS direct called him an ambulance because they were concerned he was very dehydrated.
Have you tried dyralite? (spelling might be wrong) GP prescribed it and although I had to mix it with other drinks which you are not supposed to do it did the trick with ds and seemed to clear up the vomitting/diarrhoea.
I hope he is better soon.