Achiness as a result of exam or impending labor? I am 39 weeks...?

I had a doctor visit yesterday, and discovered that I am 1 cm dilated. I have been having some achiness in my pelvic area and back on and off for a couple of weeks now, but it has been constant since last night...this has not happened with my previous exams, so I was just wondering if it could be a sign that labor is on the way soon. Thanks for any input!!