fertile cm but negative opks

We’ve just started ttc again after our miscarriage..

I’ve just started experiencing fertile cm, wet/slippery and beginning to start getting like egg white.

However the opks I’m taking are all negative, like there is barely a line there.

Is it possible to have negative tests and it spike to positive all of a sudden?

How long can I experience fertile cm before a positive opk.

Thank you!