How To Determine The Menstruation Cycle?

hi, i began taking the pill like it said on the instruction, on the first day that i began my period, right now im on the brown pills, when im supposed to get my period again, but i still haven't gotten my period. according to my count im supposed to get it in about a week and a half. is this normal? or should i get it within the 4 days of the borwn pill?