I havent eaten in 4 days?

Im 20 years old and i just cant force myself to eat, i know that i have to because I'm starting to feel really light headed and dizzy. But absolutely nothing sounds or looks good. All I've had is water and I've chewed some gum. Whenever i even think of food i get sick to my stomach. Please help i don't know what i should do. Maybe someone has some suggestions on what i can try to eat?