Nauseas headache dizzy and fatigued what could be wrong?

Many things: Unfortunately, you've just listed a combination of symptoms that can be seen in anything from sinus infection to G.I. viral infection to even an abscessed tooth as well as migraine headaches and well, you get the idea. What you need is an examination by a Dr., perhaps some lab work, and probably a steaming hot bowl of chicken soup. And of course, an apple a day once you're well.