My Son Is 9 Years Old And He Had Very

my son is 9 years old and he had very high fever for 6 days and his temp was 39.9 and for 4 days he had a mild fever of 37.7.
I went to the Doctor 3 times he checked him and said its fine. then yesterday we went to Sick Kids Hospital,
and Anton was complaining on headache and still I feel, like a mother he is not fine.
So we went to the pediatrician again he said to take an x-ray and then come back to me, he told me it can't be ammonia, it can a be Sinuses infection. he prescript antibiotics for 10 days.
The name of the antibiotic is Cefprozil.
I am so worried and it stresses me out.
My son has no clear picture of Sinuses infection, no Green or yellow Mucous
What do you think about this?
Thank you,