I'm trying to find out why I'm now 9 days late. I've always had a pretty regular cycle until the last couple of months (always 28 days) I go to school out of state, so I'm not sexually active unless I'm back home. I went home from April 19-May 15 and I got my period April 20th. I was mostly active during this time, including having unprotected sex on my period. When I returned to school, I got my period again on May 18, and June 20th (33 days) and July 19 (29 days). Now this month I just completely didnt get it, but I was only sexually active from Aug 11th-25th. I was supposed to get my period around the 18th and now I'm 9 days late. I took a plan b pill on Aug 21st after having unprotected sex, although my period was already late. Is it possible to have conceived that soon within 2 weeks or could I have been pregnant from the last time I had intercourse April-May (although I got my period)? I took a pregnancy test on the 25th and it was negative.