Condom slipped off, Help!

T

Hi ladies, me and my boyfriend were having sex this morning and we’re wearing a condom and he cummed but as he pulled out we realized that the condom was still inside of me and the cum got inside of me.

I’m three days away from my period and I’ve been having a pretty accurate cycle whether I’m a day earlier day late but I was wondering if I should take a Plan B now or if that would just be a waste ?