Confused

My mentor told me to start taking the pill when in told her I was sexually active and told me all about what to expect when I started. One of the things she told me was that my period would stop and she said she hasn't had one since she's been on the pill (the mini pill). Well tonight I got home from a night out and I've come on my period and I was just wandering if that's normal or if my pill isn't working? I use other protection anyway but if my pill isn't working I don't want to stress about taking it on time. What do??