It's normal to feel a bit low when you switch to Primal - you are 'switching fuels'. After a few weeks or even a few more is when most people start to feel great.
I personally felt great when I first started a high-fruit diet. I stayed on it for 2 years and ended up emaciated and in hospital because I had so little energy. I stuck with it because I thought it was "natural" but it was wrecking my health. Then being in hospital for months wrecked my health in a different way. Although I am still losing a little of the excess weight I gained in hospital over two years ago, after a year of Primal I look and feel way more healthy than when I was eating heaps of fruit. I was just looking through my photos from fruity days and although I looked like I was going to snap in half my face was really puffy. High-fruit works for a handful of people but fails many. I will never go there again and when someone raises the idea of trying it I get scared for them.
Primal since May 2012. Loving life and down 50lbs.