Have you considered a gluten-free diet to see if it will help. It probably will not be a quick fix, but the nausea and dizziness should improve.
sometimes these children are stressed as my little cousin had the same problems and we did all the necessary test i.e. MRI, ECG etc. which should nothing. eventually when she got some rest away from school for a month she was good as new and still doing well
my 10 yr old son was told the same and the dr gave him cyproheptad 4 mg and was sent for a EEG it came back abnormal was told not to give meds and now he is taking trileptal and is going on sept 10 for a MRI they told me he is having seizures I am still in shock