I had symptoms of dilation like the cervical pain and what not but honestly there's no way to tell. Anyways I'm 39 weeks and a fingertip dilated. I thought I would be more since I've had the cervical pain for weeks but nope.
Your doctor has to check you, I'm pretty sure. I've heard some women talk of an odd "zinging" station down there and when they went in, it turn out they had been dilating/effacing, but I experienced that sensation for about a week before I began. :-\
I went to a 3 and didnt know it and then my water broke. No contractions until an hour before.