PLEASE HELP

I was on birth control for just over a year. I quit taking it a month ago and decided I want to go back on the pill. I should’ve gotten my period last Thursday(first period since stopping the pills, minus the period I had on the placebo pill week). I still haven’t gotten my period.

First question, is it normal to not have regular periods when stopping birth control? Or should they be regular again right away?

Second question, with me wanting to get back on it, when do I start my pack? Should I keep up how it would’ve been if I didn’t stop or should I wait for my period? What if it skips the whole month?