Hello!
Thank you for the query.
It is really hard to diagnose your problem not being able to perform physical examination. Generally abdominal pain is very non specific symptom and can indicate many issues.
The reason can be chronic intestinal infection (bloating, constipation, diarrhea), peptic ulcer (upper middle pain, appears after a meal), gallstones and
pancreas inflammation (middle or right upper pain radiating to the back),
urinary tract infection (back pain, lower pain, frequent urinating, burning while urinating),
diverticulitis (lower left abdominal pain,
chronic constipation) and even colon cancer (weight loss, constipation and diarrhea alternately,
blood in stool).
If you are older than 50, please start your diagnostic with colonoscopy, abdominal ultrasound and blood work.
If you are younger than 50, stool test, abdominal ultrasound and blood work should be done at first.
Hope this will help.
Regards.