Do You Get Periods While On IUD?

i got the 5 year iud after having my daughter and it'll be 4 years as of jan. i stopped having a period while i breast fed my daughter and they said that was normal for some people and i haven't really had a real one since i had her. this week however i have had a full period and it worried me since i haven't ever had one like that while on the iud and i wanted to make sure everything as ok