I started my period Monday June 27 and it ended Friday July 1. I had unprotected sex Sunday July 3 and took Plan b about 18 hours later. I then had unprotected sex again Thursday July 7 and did not take Plan b after. Sunday July 10 I had spotting/brown blood. Is it possible I am pregnant because I had sex 4 days after taking Plan b, or is it not possible for me to be pregnant since I've had this spotting/brown blood?