You feel dizzy and fatigued, very likely, due to dehydration. (this used to be called Atkins flu). When you cut carbs very low it is a natural diuretic, you pee more and excrete more Sodium. So you need to make sure that you increase your Sodium intake and up your fluids. Easiest way is to drink a cup of stock, home made is best but a stock cube will do.
I aim for 20g carbs a day, virtually all from green leafy veg and salad. And I’m the healthiest I’ve been in decades.