What Causes Dizziness, Headache And Vomiting?

I've seen a doctor yesterday and he told me that I may had mononucleosis, I have drop of energy, lot of headache those are stronger when I move, think, do any muscular movement even like eating and sometime I'm dizzy. I had vomit about 10 day from today and since then it started. When i'm sleeping I feel kinda fine but If I try to stand up I feel a huge pressure on the head.