I don't like the dark blood in your stool. If I were guessing, remember I'm an accountant, I'd say you might have a stomach ulcer that is bleeding. The reason why it isn't black on the way out is you are missing 5 feet of your intestines. Plus they treat some ulcers with antibiotics so when you miss taking them it's worse My father had a bleeding ulcer and felt no pain in his stomach. He was loosing blood from somewhere and they went looking for the source.
I think you are right. Something is probably wrong and it needs to be investigated.
I have lower left sided pain from my j-pouch and think that's either gas or cuffitis related.
Have you had an endoscopy lately?