That sounds similar to my situation. Last week I was having what just felt like period cramps. I was also having some sharp pains. I went to the hospital just to get it checked out and found that I was having contractions. I had no idea. I guess the cramping pain was the contractions but they also said I was having 'irritablities' but the main reason they considered it preterm labor was because I started bleeding a little and I was dilated to a 1. Anyway, they were able to stop the contractions with magnesium. So if you are really concerned with the cramping you should get it checked out just to make sure. If they are continuous then it might be contractions!