birth control after birth. help!

So I just got my birth control after giving birth. It's barely been 3 months. But I barely got It today. I got my period twice on march. Baby was born on January. ANYWAY I forgot to ask my dr this question (damn you baby blues) lol. My question is, I haven't gotten my period since march 21. I read I should start the first pill on a Sunday the first day of your period. BUT I wanna start sooner haha. My question is, will it cause any infection or something if I start taking my bc pill sooner than this upcoming period? Since it's after giving birth unlike when you haven't had a baby. what do you ladies think???