Pregnancy scare!!

So, I'm on my period and my boyfriend and I were having sex. We weren't using a condom, because up until today he's been perfect about pulling out. (Yes I know you can get pregnant from precum) he started cumming as he was pulling out. My period is supposed to end in two days, I'm supposed to have two more days and then comes my fertile window( according to my eve period tracker). I know sperm can live for a few days , should I go take plan b just in case or are the odds small enough to chance it?? Help please!!