birth control
"I was excited to get it, but the insertion was very, VERY painful, even with local anesthesia.  I bled for a long time and it was very uncomfortable to sit in certain positions.  My periods were very different, with prolonged bleeding (not the short, sweet periods the advertisements promise).
I also noticed that I had started to smell badly down there.  I kept going to the doctor for it (the other doctor who cared for IUD patients, not MY doctor) and he kept telling me that it was a "bacterial imbalance" and not related to my IUD.  It most certainly was because my cervix was always open from the string.  This ceased after removal.
Also, it does not prevent conception.  It causes fertilized eggs to be discharged because they can't implant."