How long does the flu last?

how long does the flu last? i started throwing up monday and its been down hill ever sence. but today i havent thrown up but im still feeling nuseas, dizzy, back pains, tired and a bad headach and i really want to go back to school tomorrow because im going to have alot of work and i just want to feel better. should i be able to go to school tomrrow?! what are some good foods to eat while having the flu?? i have been eating saltines, soup, and oat meal and have been drinking water and ginger ale. but i still throw up. and i hate throwing up. please help!!