Posting for advice as I am at my wit's end with a strange vomiting bug that affecting my ds12 and dd7 for months now .I've been to the doctor several times who has put it down to being 'just a virus' but I feel there has to be a cause.
It has been following a sort of pattern - every ten days or so one will vomit out of the blue ( ds will say he feels like he is going to vomit about ten mins later he will, dd will complain her throat is sore and again ten mins later or so will vomit). They will then vomit several more times over the next few hours and then will be perfectly fine for approx 24 hours and will then again vomit several more times in a row and then all better till the cycle occurs again ten days or so later .Each incidence last 2-4 days .Neither will have diarrhoea but will have incredibly bad smelling wind.Neither complains of cramps or stomach pains.
Sometimes one will be unwell at a time or at other times both will be unwell at the same time like now 
There are three others in the household none of which suffer from the same thing.I am at my wit's end they have missed weeks of school not to mention all the weekends and bank holidays they have missed out on due to illness. I've wracked my brains and can't think of what could be causing it both have good hygiene wash their hands etc I've changed their toothbrushes regularly, they haven't eaten anything new or being abroad recently.We have a house dog and poultry too but the kids wouldn't be in contact much with them -the poultry that is.
Any help would be very much appreciated