Hi.
Thanks for your query.
Noted the history and understood the concerns.
Pain in abdomen with the medications like Daypro and Septran can cause similar pain in upper abdomen and since you have also developed diarrhea it possibly is 
gastroenteritis.
I would advise you the following in such a situation:
Get the stool tests done as the blood tests are normal.
Get an upper GI Endoscopy, 
ultrasonography of the whole abdomen and X-ray of the abdomen.
Get treated with an antibiotic and 
metronidazole if there is any evidence of an infection.
Also get activated charcoal and other symptomatic treatment like Omeprazole, antacid and 
domperidone if there is nausea and/or vomiting.
Use boiled and cooled water and the quantity should be in plenty to avoid 
dehydration.
Take probiotics, curds/yogurt and banana.