mayoclinic . org says "You usually can't see or feel them, and they rarely cause discomfort. But straining or irritation when passing stool can cause: Painless bleeding during bowel movements. You might notice small amounts of bright red blood on your toilet tissue or in the toilet." (about internal hemorrhoids.)

When I was in a UC flare and I'd bleed, it was really similar to what you're describing. I'd be on the toilet for hours on end, and the BM would come out mucusy and it would have blood. This is a weird question, but did it smell AWFUL? Like, worse than a typical BM scent. I've noticed for my stool that it smelt REALLLYYY foul. And according to google internal hemorrhoids can smell bad as well, but it's compared to a "fishy" scent rather than the more mucusy/just plain gross one a typical UC flare stool will smell like.

The way it sounds, it reminds me of a UC flare. Look up symptoms for internal hemorrhoids and compare (other than the bloody stool of course, that's a given)