What Causes Constant Headache Even After Treatment In Children?

My 10 year old daughter has had headaches now for two weeks they are so severe that she has to lie down at first I took her to the doctor because she had a throat infection then he gave antibiotics. A week later after taking the antibiotic her throat was ok but then still complained about headaches I then took her back to the doc he prescribed Zinnat she is now finished the course and is still complaining about headaches .