Good afternoon this is an emergency please answer as soon as possible

Okey, so i started taking the birth control pill ( the monthly one) yesterday but i didnt take it when i had my period because i havent had my period since november i went with a gynecologyst before and they gave me birth control to regulate my period but now im taking it to prevent pregnancy and i wanted to know even if i took it when i wasnt on my period, will it be effective?

Also when do i stop taking the pill? I would thank so much if i receive an answer i really need help