I took a pregnancy test and it was negative. i was on the 4 days of placebo pills and still havnt started my period..is this normal?

Probably: Birth control pills thin out the lining of the uterus, which is one of the ways that they help decrease the amount of menstrual flow during periods. However, bcp periods are drug induced withdrawal bleeding episodes. If you haven't skipped pills, the failure rate is very low. If the lining of the uterus is very thin, withdrawal bleeding may not occur.