Hi Based on the information I feel you have gastroenteritis. Most cases of gastroenteritis are caused by viruses and requires only symptomatic treatment, consuming contaminated foods or drinks is another common cause.Lightheadedness is due to dehydration and electrolyte loss in vomiting and diarrhoea. You do not need antibiotic and also not anti diarrhoeal agent. I would suggest you to drink plenty of water or electrolyte solutions to prevent dehydration. Add bland foods to your diet, such as bananas, toast, oatmeal and rice in small amounts every couple of hours. Avoid spicy food. Restrict meat for few days. You can take curd which will be beneficial. You can take capsule omeprazole 20 mg before breakfast, empty stomach once daily for a week. Probiotics like sporolac or ecobion will be beneficial. Drink plenty of water and juices