Will switching my birth control brand effect my period?

i just switched from avaine to yasmin birth control. im currently on the blank week of my first pack of yasmin, and on the 4th day of the blank pills. i still havent gotten my period, and usually would ahve by now. do i need to worry? i did have unprotected within the last month, but he pulled out. will the switch in brands have an effect on my period?