It could just be a virus or bacterial infection. It could also be a whole lot of other things. Whatever the case, you need to see a doctor. I know it's the weekend, so can you go to an urgent care clinic? At the very least you can get some meds for the nausea and vomiting. As usual, push the water/ gatorade type fluids so you don't get dehydrated. Hope you feel better soon. :-)