My pregnant bitch never seemed to have one in the first place, so never shed it. She is a keen self groomed so is ot possible her licking meant one could never form? she has had clear discharge for the last week of her pregnancy. Is this okay?

You wouldn't see the mucous plug it is in the neck of the cervix and only when it starts to come away is it visible, some bitches keep themselves so clean you may never see it.