Ovulation Timing After Plan B: Understanding Your Cycle

Question
My period usually starts between the 20-22 of every month with very few exceptions. This makes my ovulation time between the 1st and 8th of the following month. My fiance and I had sex last month during this time and took Plan B to prevent pregnancy. I had my period on the 15th of January as a result (5 to 7 days early). Taking this into account, we had sex this morning and had a slip up. Since I had my period early due to Plan B last month, should I have adjusted my ovulation time for this month? (having my period on the 15th would typically mean you would ovulate the 28th to the 2nd of the following month. However, I am not clear as to if Plan B effects the following month's regular ovulation occurrence which would mean that based on my regular ovulation cycle (ovulating between the 1st and 8th) then this would have been a terrible time to have a slip up (today being the 5th, which would be in the middle of my ovulation). Do you think I am safe? Or would Plan B be necessary to prevent yet another early pregnancy?

Answer
Dear Jessica,
There is no way to know for sure when you are ovulating, even during a regular month where you didn't take Plan B.  I would suggest that you take Plan B again, to be on the safe side.  It seems like you might want to consider a more reliable form of birth control.
I hope this is helpful,
Doctor Joan
Earlyabortionoptions.com
New York City