33 weeks tomorrow and already 3cm dilated and 50% effaced.

I went in for my every two week appointment  today and the doctor said I'm already 3cm dilated and 50% effaced. My husband and I were shocked. I still haven't had any Braxton hicks or contractions that I know of, and they said I would know if I have. He said we wouldn't be making it to our due date in Novemeber. Has anyone else experienced something similar?