You could have a peptic ulcer, or gall bladder issues, unrelated to the pouch. It doesn’t sound heart-related, but if you have any doubt about that it should be ruled out. If it’s one-sided it could be a kidney stone. A bit of blood in the stool might be unrelated, though the timing is suspicious - have you been straining on the toilet? Do you have any hemorrhoid symptoms? Have you made an urgent appointment to see your doctor?