"Junior Guru" 550-650 calories a day is not enough. What happens is that your body goes into starvation mode and you plateau. I've done the same thing. I lost 70# in about 7 months, and I have been stuck for about 2 months. I use My Fitness Pal and it keeps telling me I'm not eating enough! You are only 3 weeks out? As time goes on, up your calories to around 1,000 a day and see if that makes a difference.