It's just your body going into detox mode (ie: getting all the toxins out anyway they can). Your tiredness is probably due to a change in your carb intake - energy is formed from sugar and oxygen, however whilst carbs are a READY source of energy, conversion from fat to glucose is a process....your body's probably not use to having to wait for (or make) it's glucose source!
Changes to sugar levels also create insulin level fluctuations which also leads to fluctuating hormone levels....probably why you're moody/depressed...plus the "feel good" centres in your brain are being deprived of their usual sugar hit (ie: chocolate).
It'll all balance out in the end. Keep at it and keep up the water intake to flush out those toxins!