It's a really common statement here in the U.S., Angel. Well it's technically "you act like your shit don't stink" which is an insult to someone, saying they think they're better than everyone else. Also used, but less frequently is "you think your shit smells like roses" or "you shit roses, huh?"
Some people try to be nicer and change "shit" to "poop" but that just makes it comical. It's one of those things that works better with cuss words, improper grammar, and preferably a southern accent. ^_-
It's like "It's colder 'n a reindeer's balls" doesn't sound right if you change "balls" to "testicles" and "it's colder 'n a witch's tit in July" loses something if you say breast.

People I hate: people who try to make everyone else do things their way then get all offended and angry when they are presented with something that isn't their way.
Some people try to be nicer and change "shit" to "poop" but that just makes it comical. It's one of those things that works better with cuss words, improper grammar, and preferably a southern accent. ^_-
It's like "It's colder 'n a reindeer's balls" doesn't sound right if you change "balls" to "testicles" and "it's colder 'n a witch's tit in July" loses something if you say breast.

People I hate: people who try to make everyone else do things their way then get all offended and angry when they are presented with something that isn't their way.