What Is Cervix Like Just Before Period How Many Days Before My Period Is My Cervix Supposed To Open? (sorry Tmi!)?

How many days before my period is my cervix supposed to open? (sorry tmi!)? - what is cervix like just before period

I do not know if I Preggo or not, and I have recently learned that a few days before my time, will be used to float my cervix. I wonder how many days in advance that it would be.