I started my period on Oct. 9th. On Oct. 12th I had sex a few times with my bf, unprotected. Just to be safe, I bought a plan b pill and took it in the 2-3 (72 hour) after sex happened, period so that it was still effective. I didn't notice any side affects maybe some tiredness. It is now Oct. 20th and my period is back and its not light or like spotting its a full on period... I'm very confused. I just started my period 11 days ago & it ended the 13th due to sex. Now, I have it again? Seriously confused.