The pill changes period???

I just started taking combination pills a little more than a week ago. According to my calendar I’m supposed to get my period tomorrow but since I’m taking the pill now will my period be delayed until I get to the row of placebo pills? Or will my period start at normal time and I’m just supposed to skip to the placebo pills when my period starts? I’m really nervous about this because I started having sex without a condom and I’m kind of paranoid that I’m pregnant so I really want my period to come on time