Hello, just a thought...If your intestines are stretched this may be secondary to the constipation/sluggish bowel due to the redundant colon, and if you say you having diarrhoea you may actually be experiencing overflow where the liquidy stool is just bypassing the constipation.
My 3 year old daughter also experiences this right sided pain on a daily basis from a redundant sigmoid colon and we are awaiting a gastroenterologist opinion.