It's not a matter of training your body to burn fat FIRST. Because excess blood glucose is toxic, and carb consumption results in increased blood glucose, your body is obliged to either burn or store carbs as they come in. In brief, carbs will pretty much always be used preferentially.
What you're trying to do is limit carb intake so there isn't extra blood glucose to store, plus train your body to access fat efficiently so you don't have energy dips when the blood glucose from carb intake runs low. Eating low-carb forces your body to run on SOMETHING other than sugar, which is where burning bodyfat comes in. Most bodies will figure out how to do that within a week or two. Some people, including me, take a lot longer (think 6-8 weeks) to transition.
2 weeks is nothin.' A lot of people lose *weight* that quickly when they go primal, but most of it is water weight (because carbs make you retain water) rather than fat. If you weren't retaining water for whatever reason, you wouldn't see that dramatic drop. Give yourself some time!