Perhaps you should figure out your calories one day and see what you are taking in. Also make sure you are getting enough calories. It could be either/or.

Also, are you measuring yourself? There have been plenty of times when I don't lose weight, but I do lose inches. Everyone's body is unique and you may lose weight differently from others. Also, it takes the body awhile (especially if you have dieted before) to accept a new way of eating and give up its fat.