Hi.
Thanks for your query.
Noted the history and understood the concerns.
The commonest causes of bowel movements immediately after food are one of the following:
Inflammatory focus in the intestines or around the intestines like lymph nodes,
appendicitis,
diverticulitis.
Another reason can be IBS that is
irritable bowel syndrome.
Intolerance to certain foods, beverages and so on.
Hence I would advise you the following in such a situation:
Get the stool tests done for three consecutive days.
Stool tests for CBC, thyroid and liver functions.
Ultrasonography to start with and CT scan of the whole abdomen to confirm or rule out some of the disease mentioned above.
A course of an antibiotic,
metronidazole can help to solve the issues.
If there is a surgical cause like diverticulitis or appendicitis one surely needs a surgical correction.