I took the pill about 3 weeks ago, I've had a pregnancy test which came out negative but I'm now 8 days late and no sign of my period.

Everywhere I've read says the earlier you take it the more likely it is to come a few days earlier but this hasn't been the case for me (don't know how much accuracy there is to that). I had no PMS symptoms either up until the weekend that just passed where my breast began to ache.

I'm going to take another test in a few days - but is this a normal side effect of levonorgestrel?