Suggest Treatment For Persistent Bleeding

I have had a mirena coil fitted for just over three weeks to help with continual bleeding. For seven months prior to that I was on 30mg daily of norethisterone which I have now not been taking for two weeks. After being on the norethisterone for 5 months the bleeding started and has continued daily since the middle of October. I was discharged from the hospital when they fitted the coil in December but I am concerned that the bleeding is not stopping. It is much lighter this week but still a nuisance. How long is it safe to bleed for and will I be getting low in iron etc.