Openness of cervix

Hubby and I are TTC baby #2 so I've started tracking temp and taking OPKs. A few days ago I decided it wouldn't hurt to also try and track CM and position/openness/firmness. But I just can't find the opening 😩 it's been pretty high and I think it's been pretty firm but still struggling to figure out if it's open or closed. If I am feeling the right thing it feels closed but I'm in my fertile window according to glow so I thought it should be opening up some at this point. Can anybody help please?! Would I be able to stick my finger in it if it was open?