Hello WCTD
There are lots of possibilities as to why you're struggling. First and foremost, a couple of weeks isn't that long - it might take a couple of months to fully adapt.
The good news is, there's lots you can do to ease the path to adaptation. Firstly, re-read this thread - follow the links various of us have posted; there's lots of info out there but it takes some digging to find it.
Don't be afraid to eat more fat. Fat helps satiety - which will reduce your hunger issues.
Drink plenty of water - and put salt on everything! Turns out, salt is really only a problem (hypertension) when it's in conjunction with carbs. Once you reduce carbs enough, your body will dump salt (and also potassium, and magnesium) and this loss of electrolytes can make you feel pretty crappy ( so called "keto flu" ) so keep your electrolytes coming.
Don't stress the loss of performance. It
does come back - your body will learn, it will adapt. I've been low carb since New Year, and after a month of being pretty rubbish, I'm now happily lifting weights, and riding longer distances.
As they say on reddit/keto - "Keep calm and Keto on"