HI EXPERIENCED DOG BREEDERS *ONLY*?

hi my staffy is around 60 days pregnant and we just saw a clear gooey thin line of mucus coming out of her vulva and last night she vomited 3 times but then she re-ate so wat does the gooey stuff mean also don't say we know nothing about dog breeding we are registered breeders of neapolitan mastiffs and one of them is an Australian champ and have delivered healthy litters its just that our last litter was 6 months ago and i completely forgot about signs of labour so /////// what does the mucus mean.??????