4 words you never want to hear.

Okay just so you know, it IS NORMAL for a period to start one day later than you expected it. She could've counted wrong on her calender, if she even does that. If you're on birth control, which she should probably be if she's sleeping around, then you know when it's gonna start. As a girl, the date your period is "supposed" to start is sometimes a guesstimate, she could have been stressed out, that can sometimes cause you to skip a month. When I wasn't on birth control, I was just going by weeks, saying "okay it's been 3 weeks, I should be starting soon." Girls don't always count by days. She shouldn't have freaked you out like that so soon, she should've gotten tested first or something.