What Causes Headaches Along With Abdomen Pain In A Child?

my daughter has been complaining of headache and tummy ache for several weeks. off and on her throat hurts. She has been to the Dr a few times over the last few weeks. She was treated for strep, thejn tested after she was done with antibiotic and it was negetaive. She was treated for a sinus infection although I don t know that she even had one. Mono test showed she has previously had it but does not currently. She had other blood work done also and everything turned out fine. Any thing else I should have checked out for her? She is 10 years old.