Started Birthcontrol two weeks ago and i got my period

Hi guys I’m just concerned because I recently started birth control and i’m in my third week in the pack, so my period shouldn’t come till next week. However today I started my period, and I’m not sure if why but I do know that today I supposed to be my period if I hadn’t started taking birth control this month. Is it normal to get your period before the “period week” if you just started using it?