I've got so many!
I've had some bad experiences with BM growing up, severe constipation mostly. When I was 19, I went to lunch with some family and they ordered a big sushi platter. I was basically homeless at that point, so I chowed down feverishly.
Fast forward to that evening. I have a really bad guy pain, the kind that only goes away after a 20-30 minute session at the iron throne. The build-up of gaseous pressure was trapped, nowhere to go.
20 minutes go by and I can tell I've got my work cut out for me. While very pleasant, the Macy's bathroom doesn't have what I need. The sweats start kicking in from the pain.
So what do I do instead? Head to Safeway, purchase a name-brand enema and head straight from the register to the single stall restroom.
I had a few enema as a child, for constipation, but had never done it to myself at this point and don't recommend it, at least not in this situation. I am perched on the toilet. I Insert the tip. I squeeze.
I did something wrong, because it was shooting onto the wall. So I repositioned and pushed a little further in. I squeeze again and this time it seems to go where I intend. I feel a bit cooling sensation, which quickly turns to a sharp burning (like spicy shits).
At this point, it feels like my ass hole is about to rip apart and, frankly. There is nothing I can do. This enema has provided adequate lubrication and nothing was going to stop this bunker buster.
I bite down on the drawstring on my sweater and try to hold back. My sweat has turned cold. I can tell my face is pale. Asshole destroyed. At some point, I just stop holding back and decide to get it over with.
The result? The largest BM I've ever had and the most blood I've ever had come out of my body. But, aside from the stinging anus, I felt much better. I wiped up, flushed, clogged the toilet, packed some TP in my briefs and got rid of the evidence.
Met back up with family about an hour later, pawned it off as mild food poisoning. Walked around for a few more hours at the mall. Spent the next couple weeks trying to let my ass heal.
Since that incident, I started a "routine" so this would never happen again. It has worked well so far!
However...one night, 8 years later, I would go drink with friends in the woods. A combination of a lot of alcohol and coming down with the flu, caused diarrhea so explosive, that I came home the next day with a (self-diagnosed) thrombossed hemorrhoid.
It coincided well with the 2 weeks straight of diarrhea and 3 weeks of coughing attacks (self diagnosed whooping cough).
I just told everyone at work I fell and hurt my back. I wish I could have been in medically induced coma for those 3 weeks. It was so bad.
Tl;dr: Ate too much sushi, got constipated and ripped my anus apart. 8yrs later had explosive diarrhea and gave myself a thromossed hemorrhoid that lasted nearly 2 months .