I have never heard of one "breaking"...the way they are constructed it would be pretty much impossible but they can get "lost" and :forgotten" and pushed up inside of you. It happens more times than you would think and if you suspect that may be the case make an appointment with your gync. asap because it can cause toxic shock syndrome and don't be embarrassed because I've heard it happens to a lot of women!
the string can come off , so yes. you need to go to the doc and have them remove it. this has happened to me;/ it can make you sick.. if you wait to long your body will reject it after it breaks down,& will have discharge that looks like gritts. but go to the doc they might give you meds to fight infection and it will move this along faster..