You are effacing and dilating. Some women start dilating weeks before delivery and for others it's a sign of pre-term labor, especially if you are experiencing contractions. I am almost 33 weeks and have been 3cm for 2 weeks now. I had pre-term labor last pregnancy, so as a precaution, I've been on bedrest since 25 weeks.
But at this point, your body is just preparing. Just take it easy over the next few weeks.
I was the same way with my last, 1cm dilated at 33 weeks, I had him at 35 weeks. BUT every woman's body is different. I have a friend who is 29 weeks and has been dilated to 3cm for weeks now and doctor's are doing nothing to help her from delivering prematurely.