I've known women who have had occasional contractions for the whole last month.
If you are noticing a decrease in movement, I would call your doctor and ask to be seen- cramps are pretty normal, but the lack of movement could be concerning. Also, if the cramps are coming and going with regularity, are getting closer together, and getting more sever- you will want to start timing them as contractions. If they aren't doing that, it's just normal aches and pains and your body prepping for labor.