Hi dunrena, it's normal to feel a bit low because of the shock of diagnosis, and maybe you need a little time to get used to your diet. When I was first diagnosed I dieted quite hard; as a result, my blood sugar was often in the threes, and I would feel quite down and dozy going to work in the mornings. A little more fat in the diet helped there- I started having a boiled egg (or two) for breakfast, and some sardines or almonds/ sunflower seeds during the day, and that picked my energy and mood right up again.
The other thing that will help is that you may well start feeling healthier and better as the weight comes off, or as your sugars come down. Of course, different people get better at different rates, but I wouldn't be surprised if you start feeling better sooner than you might expect. There's no real 'upside' to diabetes, but I must admit that I was in terrible shape without knowing it last September, and now I feel better than I have felt in 10-15 years.