Seconding the aforementioned hormonal and dietary mayhem suggestions as above. It's certainly possible that one of your old foods was doping you up on serotonin (a lot of carbs do this). Also, is it possible you're going through something analogous to a herxheimer reaction?

If you're losing weight due to this new diet, bear in mind that many of the toxins in the human body are stored in fat. (Fat is also estrogenic, btw.) When a large amount of fat is being broken down, a lot of these molecules are getting released into your body to be processed and elimited.

Whatever you're going through, I just want you to know that you're loved and supported and when you break through to the other side you will feel so much better.