Most of the time when i take morning after pills, my period comes a week after. but not this time. does it mean the pills do not work?

No: Does not mean it did not work. The only way to find out if it did or did not work is to have a pregnancy test around the time your menstrual cycles is due. Please, please do not use the morning after pill as a method of contraception. Talk to your doctor about using a better method. Morning after pill is great for emergencies, but should not be your routine contraceptive.