Hi. Thanks for your query. Noted the history and understood your concerns. Fast food particularly pizza can cause gastroenteritis hence causing the vomiting and loose motions as you have mentioned; this being repeated after you ate again indicates the possibility of intolerance too. I would advise you the following in such a situation: Stop eating outside food and particularly anything like pizza. Boiled and cooled water and home-made fresh food only. Send the sample of stool for test. Consult your Doctor for clinical evaluation and examination to get you started on a proper medication which may be an antibiotic active against intestinal infection. PPI like Omeprazole. Domperidone to stop vomiting. Antacid for gastritis. Probiotics and symptomatic treatment can help you further. Electral solution for replenishment. Plenty of oral fluids and you will be Okay.