is it normal to skip period on bc?

I've been taking birth control for almost two months and i am sexually active with my boyfriend, but is it normal for my period to be skipping? Im a week late as of today.  My last period lasted longer than normal bc of the last time i skipped my period so there was older blood coming out as well as the new blood. I'm just concerned because i thought the pill was supposed to make your period come on time.