C.L.
I have Mirena too...going on 3 years. I've had all kinds of crazy flow schedules since I've had it...from no period for months to bleeding/spotting for several weeks. My doc said the bleeding/spotting is okay for up to 4 - 5 weeks. If you continue into the 6th week, you should be concerned and call the doc's office for an appt. Unless the bleeding is very heavy, then call after 2 weeks.