What Causes Abnormal Vaginal Bleeding After Mirena Insertion?

Question: I got an IUD placed a couple of months ago...the Mirena. My first month I got my usual expected period on day 28, but it lasted for 15 days. I was told this was normal. My second month, again. Got my period as expected, it too was lasting longer than usual. On around day 14 I passed a large ping pong size whitish piece of tissue, it was like gristle. So. Made an appointment with my OBGYN, he said this was normal and it was my body adjusting to the IUD, at his point. Told him to remove the IUD. I continued to bleed, but it was getting heavier and I was passing large clots.,around day 19 my period was heavier and it was dripping out of me, I was soaking through tampons and pads and the clots we're getting larger. I went to the ER where they took my history forr the past couple of weeks and gave me a presciption for,Provera, I have been taking this now for three days, the situation is not getting better, I am soaking through a tamplon and a pad every two hours and this morning I woke up in. A pool of my own blood. I was wearing a tampon and a pad too. I called again my OBGYN they said to give the Provera a chance to work, it can take up to a week. My concern is that I am usually anaemic anyway and this could make it worse. I have a few questions but mostly how do I find out what is causing the heavy bleeding and the clots. I have had to kiss three days of work because it is flowing out of me. The nurse told me that because of my aneanmia if I am still bleeding on Friday to call them back. I do have a follow up appt with my OBGYN next Wednesday.

I am 41 and had my last baby three years ago.. Last summer I did have a miscarriage at 9 weeks, and my doctor recommended a D&c because of my anaemia. Following that procedure he asked about birth control. He recommended the Mirena so a couple of months ago I had one placed and that is when all this began. I had the Mirena 10 years ago and had it removed two years later, when we trying for another baby.i had no problems with that one My son is now,three years old. My cycles,have been regular with mild to moderate clotting and cramping. I am 5 ft 5 inches and weigh about 170lbs. I do not smoke.