The most common side effects of an IUD are irregular bleeding (metrorrhagia) and prolonged menstruation, also called menorrhagia. It is difficult to know whether or not you experienced metrorrhagia or a regular menstrual period when you were bleeding on the 17th of January. However, it doesn’t seem likely that an IUD can be expelled from the uterus spontaneously. Sensations of “movement inside the cervix” may be a part of the IUD that normally sticks out of the uterus through the cervix. The other, bigger part, of the IUD remains inside the uterus. If you're having trouble with the IUD, though, you may want to visit your gynecologist's office.