I've had only 1 condom break, and one condom slip off. The one condom slipped off because it was one of my first times (long ago). 1 condom broke when I was doing missionary, and it slipped out, and got stuck between the rough couch and the ass. Other than that, in the 1000s of times that I've had sex, nothing happened, no leaks that I know of or anything.
The breakage rate is supposedly between 1% and 5%.