Yes! You are in the process of adapting your body. Before, you were burning carbs for fuel. Your body can only store a limited amount of energy that it gleans from carbs - hence why you need to 'carb load' before a significant amount of exercise. Runners who talk about 'hitting the wall' or cyclists who talk about 'bonking' are all referring the point at which their bodies run out of fuel.
That's why all those energy bars, drinks and gels for athletes exist.
However, when you have switched your body to burning fat, you will have an unlimited (practically) source of fuel. Even elite athletes will have enough body fat to sustain serious exercise.
You need to give yourself a bit longer, make sure that you're keeping your diet low carb - don't fall into the trap of thinking that you need to add extra carbs for your exercise - and you will find that it gets better. If you've been doing it for a couple of weeks already, it should get better for you soon.
It's really worth reading this book:
The Art and Science of Low Carbohydrate Performance
These guys do their own research into the whole thing, and this book is specifically written for serious athletes - although it's just as applicable to any of us who are low carbing and wanting to exercise.
You may even find, actually, that your exercise gets easier and your times get better once you're keto adapted!