What Causes Recurrent Fever In A Child?

My eight year old daughter has a recurring high fever (104) for the past nine weeks. She will have the fever with flu-like symptoms (fatigue, vomiting, headache) for 4-5 days and then it will go away only to return again a few days later. Same symptoms, repeated for the past 2 months. She is ordinarily healthy. Allergic to wheat. She has complained of her back/spine hurting for 2+ years. In the past two months she has been diagnosed with pinworm, inner ear infection, outer ear infection, and flu -- all with the same symptoms. She has tried 2 rounds of antibiotics, to no avail. She is currently on day 2 of another round of 104 fever, fatigue, vomit and headache. Thanks for your help!