What Causes Headaches And Fever?

My 5 year old daughter has had a sudden complaint of headaches and is now running a 102.8 fever with out any relief from Childrens Motrin. this isnt the first time that she has had sudden prolonged fevers out of no where that could last up to a week. her pediatrician always state that she is fighting off some kind of infection however I cant understand why it happens to her at least twice per year. I think that there must be a better explanation of her condition.