What can cause chronic diarrhea, crampy pain in right mid abdomen accompanied by a rash all over the body?

Lots of things: If the rash is itchy , the first thing i'd think of is celiac disease / dermatitis herpetiformis. There are a bazillion other possibilities.

Needs detailed w/u: Usually, chronic or recurring abdominal pain is functional pain. Symptoms that require a doctor’s immediate attention include a high fever, loss of appetite or weight, pain that awakens the person, blood in stool or urine, jaundice, severe nausea and vomiting, difficulty swallowing, and swelling of the legs and/or abdomen. The hist. provided is minimal, with more detailed Hist./P/E needed. See GI