question about the IUD

I have had it for about 3 months now. Everything's been fine. If I have had a period, I just bleed a little and maybe for half a day. I went for my first checkup with it just last week and the doctor said everything looked good. It hasn't moved or anything. Well this morning I woke up and I am bleeding about like a normal period was for me before I got it, pretty heavy. Is this normal?