I took a dump in the broken toilet at work and damaged it even more.
Why did you poop in the broken toilet? By accident?
I've been constipated at work for the whole week. I couldn't hold on any longer so I took a dump in the broken toilet.
You really made the job worse  for whoever has to clean up that toilet. You should next time think about others and how they would feel having to clean a broken toilet.
You're overreacting. It's only a toilet.
There's only one thing to fix what you've done. Go back and clean the toilet and offer to help fix it or pay for the damages. You should confess and get it over with, as embarrassing as it seems.