Suggest Medication To Postpone Period

Hii am gonna c my boy friend on 25/12 to 1/1 and my period was supposed tp come on December 12 but it didnt come..I know i am supposed to take the birth control pills on the first day on my period..I dont know how to take this pills now..we are already usin condoms but I feel more safe when I use those pills..I wanna take the pills that postpone my perios and yasmin (birth control) pills.Please tell me what to do.