Where is my period?

completed one pack of Mylan's Levonorgestrel and Ethinyl Estradiol extended cycle (91 tablets). When it came time to take the placebo pills, my period never came. I stopped taking the pill in case I did get pregnant somehow. All pregnancy tests have been negative. I am now sitting here one month later and still no period. I recently started cramping and feeling like a period was coming, but it never did. I am usually a very regular 28 day cycle person. Is this normal? Has this happened to anyone before? Thanks again!