Help! Is this normal😓

So I had my period on the 5th of November and that’s when I started taking the Yasmin combined pill. I then had unprotected sex on the 11 November. The pill says if taken properly it’s effective immediately. I’ve been getting really dark blood like spotting since I finished my period (12 November) which is really unusual. I’m going to take a test this Saturday. What could this be?!