39wks/2days. totally effaced but just became 1cm dilated. how fast can i end up getting to over 4cm? also what are the chances my water will break now

Higher !: As your cervix effaces and dilates there's a higher chance that membranes may rupture. On first pregnancies the time between initial dilation from 2 to 4 cms may take over 24 hours if you are not in the active phase of labor.

No rules : There are no rules as to how fast you will go into labor. Being 1 cm and effaced is a good sign. If your water breaks or you start contracting regularly then it's time to head to the hospital.