I am 37 weeks, dilated to a 3, and my doctor said about 70-90% effaced. He said anytime within two weeks he believed. I have been walking the past two weeks. Tonight when I was walking I had a bad cramp like a charlie horse where my pelvis and leg meet. They are intermittent and not constant, but they have not gone away. Could this be starting contractions?

This sounds more like either braxton-hicks contractions, however, since it is where you leg and pelvis meet it could be nothing more that pressure on your sciatic nerve.

At this point in time it is best that you contact you doctor to be sure.