When pregnant can you have listeriosis without any symptoms? Or will you always have symptoms? Is stuffy, runny nose a symtpom?

Not likely. Asymptomatic infection is rare. Usually diarrhea, not sniffles. From a medical textbook: "Obstetricians may receive calls from pregnant patients who ate food implicated in an outbreak of listeriosis that frequently receives wide media publicity. It is reasonable to reassure the asymptomatic patient and to recommend cultures of stool and blood for patients with any symptoms, including diarrhea."