Are you incorporating ALL the Primal lifestyle changes - sleep, slow movement, stress reduction, play, LHT, etc.? What you eat is important, obviously, but it's definitely not the only piece of the puzzle. HEALTH HEALTH HEALTH, not WEIGHT WEIGHT WEIGHT.
Also, remember, that everyone trying to lose weight is *really* trying to improve their body composition (ratio of lean mass to body fat). Even if for a lot of people it's FAR more about fat-reduction than muscle-growth, still, for everyone, we are talking about body recomp. Thinking about it that way may help you focus less on WEIGHT and more on FAT LOSS + MUSCLE GAIN
Also, give yourself a break; it took you years of eating a certain way to get to your starting point and you aren't going to turn that around 100% in 21 days.
Hang in there and focus on your health!
“If you want to build a ship, don't drum up people together to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea” -- Antoine de Saint-Exupery