Plan b?

He came in me last night and this morning. This morning, We got breakfast then got the pill to be precautious. I’ve never taken a Plan B before, I don’t have any kids and have never gotten pregnant. I just ended my period yesterday but I’m still spotting. Should I be taking a plan b? It says my fertile window which are the Green Day’s don’t start until Wednesday but then it says my fertility is high today so Idk what to do I’ve never had to take one before