I have heard that flu-like symptoms are a sign or early labor...?

I am 38 weeks pregnant, 3 cm dilated, 80% effaced, and her station is -1. I woke up this morning with a stuffy nose, headache, sore throat, BUT noooo fever. My stomach is kinda choppy, and my OB/GYN told me last week that it could be at ANY time, but I was wondering just in case the flu-like symptoms are acting as a sign of early labor, how long do the symptoms usually last before actual labor begins??