Just started birth control

Alyssa • 23.
So I started my period on Thursday & Started taking birth control pills for the first time in a year on Sunday. I won't be seeing my boyfriend until Friday night and we, of course, plan on having sex. He wants to ejaculate inside of me, but I'm not sure if the pill will be strongly effective by then? 
​I've been reading mixed answerings saying it's effective right away, within 48 hours, after a month of taking it. Opinions?