I didn't miss a pill the whole cycle. I took it between 7-9AM each day. I usually get my menses 3 days after the last pill, it is now the fourth day and there is no sign of my menses. This has never happened before.

I had sexual relations on the 27th, 28th, 29th of December. The last of my pills that month was to be taken on the 1st of January.

Would pregnancy be possible? What could be causing this delay?