Pregnancy ?

Last period began on July 3. That would put me ovulating around July 16-July 21, I believe. On July 21, I got engaged. That night, we didn't have a condom, so we did anal (stupid, i know, especially without a condom). He didn't come in the anus, he did it right towards the top of my butt. IMMEDIATELY after that occured, I ran to the shower to wash off everything, because I did not want sperm dripping towards my vagina. I was really paranoid because I might have been ovulating on that day (it was possibly the last day). I kept washing off and wiping just to make sure, because we didn't use a condom. Since I was so paranoid - On July 23, within 48 hours of the.."act"..I took Plan B. Since I took it after ovulation, how could that affect me? Most importantly, could I possibly be pregnant? My next period is due August 31 or around that time. Could Plan B make me late? Again - Could I be pregnant?

Again, I know the chances of bacteria and STD with anal, without a condom. Fiance is only parter I've had, and vice versa. I strictly want help with the Plan B and Pregnancy issue.