17, missed pill. need some help and advice.

I have been on Cerazette for just over 3 months. On Saturday night I forgot to take my pill and I had unprotected sex on Sunday morning (around 10/11). I took the missed pill at around 4pm on Sunday and then my pill as normal at 10pm.

Today I have had some spotting. I don't know whether I should be worried about pregnancy or not? I tried to call Family Planning today but they weren't answering their phone and I couldn't get an appointment to see the Nurse at my local surgery, so it's probably too late for Plan B now.

I need some help and advice. Thanks