Hi.
Thanks for your query.
Noted the history and understood the concerns.
Sudden excruciating pain in abdomen along with nausea, vomiting and diarrhea can be due to the following reasons:
As your Doctor has told you, intestinal infection.
Any intra-abdominal pathology like
appendicitis,
cholecystitis,
diverticulitis and so on.
This can be diagnosed by the following ways:
Clinical evaluation by a
General Surgeon, examination an investigations:
Tests of stool and blood, gives the best idea.
CT scan as advised, if not being done in a routine way go to ER and get the investigations done.
A course of an antibiotic active against intestinal infection,
metronidazole and probiotics.
Drink only boiled for 20 minutes and cooled water.
Plenty of oral fluids. Soft bland diet.
Review with your Doctor after 5 days to have proper clinical evaluation, investigations and management as required.