Hello
First of all you didn't mention your age , sex and duration of headache ( days , months or years ).
But few common causes of headache with
dizziness & nausea may be due to these possibilities , these include:
1 Hyper tension or
hypotension , get in physical examination at the time of headache and these symptoms.
2 Hyper acidity , as you mentioned that there is dizziness and nausea with
abdominal pain may be due to hyper acidity . Diagnosis can be confirmed by clinical history and physical examination.
3
Migraine may be the another cause of such symptoms .
However , there are so many other reasons of such symptoms like anemia ,
low blood sugar level , tension , anxiety , over exertion .
In my opinion consult a physician and get his opinion .
Even eye sight defect causes such type of symptoms.