Which day should my period start?

My period never starts on the day of the first white pill. It usually starts by the end of the next day. Me and my boyfriend don't use condoms anymore, and he pulls out. I'm always scared the day of the first placebo pill that I won't start at all. It's my fourth month. Also, I had a little breakthrough bleeding a couple days ago, but it was literally one dot and it was red instead of brownish. Is it normal to start after a few days of the placebo pill?