I had similar symptoms.
I am not a doctor and I cannot diagnosis but I will share my experience:
Extreme pain not long after I ate.
Diarrhea.
My daughter was an Registered Dietitian at a university hospital. (Virginia)
She later became a physician’s assistant and asked what my GIs treatment plan was:
1. Biopsy
2. Breath test at a hospital
3. Allergy testing
4. I don’t remember!! long ago😇
I was diagnosed with celiac disease.
Allergic to wheat in any product!

What a relief. Just eat gluten free. Phew!
Gluten Free For Dummies is a great book: my bible which I have memorized.

OK, I am not perfect. I have a favorite candy and I over indulged in it: Guest what!
After consuming a LOT of these candies I paid a penalty! Montezuma’s revenge. This candy contains wheat!!

Celiac is easy to manage if you read the label ...
And do not eat anything with wheat in it😡even favorite candy.
P.S. I wonder if I could eat one or two a day🤫