Thanks for posting your query.
With the available described symptoms, you are most likely suffering from Acute viral gastroenteritis
Presence of abdominal pain
along with watery diarrhea suggests the diagnosis.
You should consult with internal medicine specialist/ gastroenterologist and should go for thorough check up.
You should also go for complete blood count
, serum electrolytes, renal function test.
You should take complete antibiotic course, probiotic
You should maintain your hydration by taking potassium rich solutions.
Avoid milk and all milk related products.
As such there is no correlation between hiatal hernia and gastroenteritis.
Dr. Mayank Bhargava