My period was due 20 days ago but hasn't arrived! Around the time it was due I had a bit of spotting but nothing else. I took a pregnancy test around 10 days after it was due which came back negative, but 10 days on I've still had nothing so I'm worried. I have the Mirena coil, so I know it's only a really tiny chance that I'm pregnant, but I can't think why else it's so late? Any help?