Try upping your sodium if you have no medical reason not to.

Lack of salt intake makes me lethargic. Legs of lead on my walks. Seems pretty common with very low carb intake. Carbs cause the body to retain fluid. Lack of carbs cause the body to flush fluid thus the typical "water weight whoosh" in the beginning. The favored amount I read most frequently is 3000-5000 mg of sodium. Some people seem to need more. I'm fine most days at the lower end but have definitely experienced a need for more than my typical when I string together several days of rigid keto (I'm more flexible with carbs now than many here are).

Some folks favor chewing on salt crystals. Some make salty drinks (ketoade). I just pour about a 1/4-1/2 teaspoon in my palm, lick it off and wash it down with a swig of water. Many drink salty boullion. I do that in the winter and add extra salt. In the summer time, in a pinch with no water available, I'll chew on a boullion cube. Might be a bit much for some folks but it is effective for me. I'm not a lover of all things salty so have experienced "the need". I have cubes in my purse, back pack, car etc. Just in case.