Cervix position high AF due tomorrow confused?

Ok so AF is due tomorrow I've tracked cervix through cycle and its be text book positions 3 days ago it's was low felt today and it's right up high I can barely feel it I haven't tested yet as I promised myself I would only test if (when) late but as cervix position is an unreliable pregnacey prediction I'm now wondering whats happened  as It should be low, any ideas or previous experiences with cervix and bfn bro? Thanks ladies :-)