Can be period be late from taking Plan B while on my last period? While having sex, the condom broke so I took Plan B that night. It was only the 5th day of my period but I took the pill just in case. The pill caused my period to last a week and a half lo
One. One of the most common side effects of the Plan B pill is that it can cause cycle irregularity no matter when you take it. It is great that you took the Plan B right away since the sooner you take it, the more effective it is in preventing pregnancy. Since you took the Plan B on the same day you had sex and you were still on your period, it is highly unlikely that you would be pregnant. I attached a website with some excellent information about the Plan B below.