One problem that would explain all of your symptoms would be migraine, with abdominal migraine.
This happens but is rare.
Dizziness is an odd expression of migraine.
It is rare, but the vestibular migraine can be independent of headache.
And can give abdominal symptoms.
The GI doctor needs to scope you and rule out gastritis.
In fact, some people with gastritis can have associated headache symptoms, and I have seen the association with migraine.
And infact, migraine can be of gastric origin.
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