I've Been Taking Norethisterone For 5 Months While My Mirena

I've been taking Norethisterone for 5 months while my Mirena coil settles in to help with my insanely heavy and painful periods (I'm 43 & this year they got worse, basically 2 months of constant clotting and very heavy period, I became anaemic, then 3 months of intermittent bleeding, 2 months or spotting - the last 5 months on this drug). I am beginning to feel better, except for awful back ache, so my consultant and I have decided I should come off the Norethisterone and see what happens. 3 days after stopping it I have started to bleed - can you give me any idea how long this will last for and how heavy I can expect it to be, also, what happens re my cycle now - given I have a coil. my consultant was very vague and just said I'd have to see what happens - but some idea would be reassuring, at least i can be prepared.