Thank you for posting.
Most IUDs stay in place after insertion. Expulsion occurs when your IUD falls out of the uterus. It may fall out partially or completely. Unfortunately, it's not always clear why an IUD is expelled, but the risk of it happening seems to be higher during your period. If an IUD is expelled to any degree, it must be removed.
What did your doctor say? If you feel this form of birth control is not working out for you, talk to your doctor about other options. Below is a list of BC methods that you can look into.