Hi Sky -
You will likely have a period around the 3rd or 4th day of the sugar pills. For example, if you start the sugar pills on a Sunday, you will likely start your period by Wed or Thurs. The good thing is, you will probably have a much lighter and shorter period than you did before.
Sometimes, though, it can take a couple of pill packs for you to adjust to them, so anything weird like moddniess or cramping might be expected as well.