Bowel habits and stool shapes vary from person to person. Certainly the variation on food intake can determine stool shape.
To ensure there is nothing going on (i.e. inflammatory bowel disease or a colorectal mass), a flexible sigmoidoscopy or colonoscopy can be performed. These are relatively comprehensive tests to evaluate the anatomy of the colon.
Gladular tenderness is associated with a variety of diseases - not just gastrointestinal. For instance, any type if infection (GI or otherwise) can lead to those symptoms.
If the GI tests are negative, and the stool shape continues, then consideration of irritable bowel syndrome can be discussed with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.