Help! One very confused lady!

Holly
So it's been 24hrs since I took the morning after pill and 48hrs since I had unprotected sex. I'm now noticing a brown/ purplish discharge in my underwear and when I wipe. Bearing in mind I finished my period 2 days ago and my fertile window begins in 4 days. Has anyone got any idea what this could possibly be? I'm quite scared, I don't like the idea of getting pregnant 😬! Please if anyone has experienced anything like this, shed some light and help me out! 
Thank you