Postpartum period with IUD

So I got the Mirena IUD on halloween, which was 6 weeks +1 day postpartum. I got my first period after having my daughter november 3rd and I'm still bleeding. Is this normal???? It's day 15 of this strange period. Someone told me it could mean that I'm pregnant?? Should I take a test to be sure??? i have pelvic pain too that I thought was due to my period.