First off make SURE you are staying hydrated since you are vomiting so regularly, and be certain to rinse out your mouth very well to try to minimize damage to your teeth from contact with stomach acid while you sort out the source of the problem.
Can you drink shakes and liquids, or does that not stay down either? You REALLY don't want to have that rapid weight loss, since it can lead to other serious health problems. Yoghurt smoothies made with frozen fruits and berries, and sweetened with frozen orange juice concentrate, are nutritious and should be easy on your stomach. Add wheat germ for even better nutrition. Don't let yourself become more sick while you try to find an answer!