My last period ended on December 18th. I got on birthcontrol on the 9th of January. So my period was supposed to start a couple days ago. Is that going to change due to the time I started birthcontrol, because of the green pills? I'm just sort of concerned. I haven't had any blood or anything and my lower back and head hurt. I was also bloated a little bit ago. Does this involve the pill? When will my period come?