Longer period - Mirena???

I got my Mirena about 3 weeks ago and I was on the pill before that. I didn't feel it at all go in and cramped slightly the next day and had discharge but other than that no issues at all. I got my period 5 days before I was supposed to though, and it's been going on longer than usual. But it doesn't need anything more than a panty liner. Is this normal? Or am I gonna bleed forever? I got it Saturday and it is now Thursday but I'm just spotting. (My periods on the pill were about a day and a half). Also, haven't had sex since I got it cuz my bf is in Philly for the summer.

Thank you!