Aight. Goto bed, have some chicken soup, you know the usual "granny's remedies" bullshit and see how you feel after a few days. If the tiredness doesn't go away, consult the doctor about it. Tiredness is a symptom of mononucleosis infectiosa. But I think it's just a little flu. Oh yes! Granny knows best! - She certainly does! Science with the nation's favourite old dear.
Heh the Kissing Disease? Tiredness is also a symptom of Hyperthyroidism, anemia, depression and pregnancy. You *have* been using protection haven't you? Seriously though, hope you feel better soon, no one likes to be ill.