Your symptoms are common, but they could have been brought on for many reasons.
First, hardly any of the weight you've lost over the past 2 weeks is from fat loss. Almost all of it is from your body retaining less water and your body having less carbs/food in your digestive system. I say that not to discourage you, but to prevent you from being discourage in the future when your weight loss slows (2lbs/1kg or less per week is considered healthy weight loss).
As far as your symptoms. They could be the cause of your body finally entering a ketogenic state (it can take some longer than others). It could be because your total caloric intake is too low (that's where the "high fat" part of the diet comes into play). It could be because you've eaten differently for so long and your body is taking time to acclimate to the new change.
For me, the stomach symptoms tell me that my body has reached ketosis. It happens all at once and usually goes away in a few hrs. Lack of energy/feeling poorly is usually from not eating enough calories.
Remember that you're making some huge changes to how your body functions and it's not going to fix itself overnight. Your symptoms shouldn't last more than a day or two and if they're still continuing you may want to see a doctor to make sure it's not something else.
