Late period?

Okay so after my period last month a week later I started the pill.. my doctor said that I may not have a period. I'm confused right now because I haven't started my period yet but I'm having bad back cramps, headaches, fatigued, and regular cramps. I am sexually active if that makes a difference but me and my S.O. don't d nothing without protection. So why no period but the symptoms? My original period was supposed to have happened the 13th.