Seriously listen to Robin about making sure you are accurately recording every calorie. I was amazed when I started doing this how fast every little thing can add up.
Also, the scale is a tricky thing. I can gain 3 to 5 pounds from morning to night, during TOM, during ovulation, or even over the weekend because I don't exercise or drink enough water. So what I do is take my measurements on the first of every month. That is what I use for real indicator is on how I'm doing. The scale is just a way to obsess, which is one of my favorite hobbies.