The problems is as a type 1, you need insulin. While at the beginning for some period of time you do make some insulin, you slowly don't. What led to your diagnosis probably would have been high blood sugars, which means you are already not making enough insulin.
To use the food/carbs you eat as fuel, you have to have insulin, that would be why you are tired. Some food is literally just going through you, you are probably even eating more food than you actually need because your body is trying to supply itself energy, But it is not succeeding until you have enough insulin to actually use it.
Even if you are low carb, your liver puts out glucose that can't be used properly, even if you are low carb, most people also need some insulin for protein and fats ( a lot lower ratio though). The tiredness should be helped after a few weeks of some insulin.