Why period is getting delayed ever after taking birth control pill?

Hormonal Birth Control works by suppressing the menstrual cycle in order to stop ovulation, no ovulation means no menstruation - the bleeding women experience while on the pill is a withdrawal bleed caused by the drop in synthetic hormones when going from active to inactive pills. It's normal to experience irregular bleeding for the first three months on the pill while the body adjusts to going from a normal cycle to this new pattern of bleeding. Coming off the pill cycles can be irregular for up to 12 months while the body gets into a regular menstrual cycle again.