Af nearly 3 days late and cervix closed?!

I will be 3 days late tomo for af and I'm never late if anything I'm a day or 2 early sometimes. Been having cramps all day yesterday and hardly any 2day and cramps in both my ovaries so I know my cysts must be coming back :-( I've taken a test and it was bfn. Been having creamy cm which I never get before af and my cervix is closed. Is the cervix supposed to open immediately before af or can it open a few days before? Also my cervix is low and firm....could all this still be a possibility?