Have you ever checked out Reddit's https://Reddit.com/r/keto keto subreddit? The keto-flu is a known & expected phase that matches the "anxiety and headache" thing. If you quit sugar "cold turkey" about 4 days in your body essentially switches from a carbs-for-fuel system to a fats-for-fuel one. It feel pretty wretched for a day. Afterwards you feel great, virtually never hungry, & weight melts off.
Can confirm that. The very first time I attempted a keto like diet (was actually a PSMF if I recall correctly), I felt so shitty and lightheaded in the first couple days that I bailed and tore into a small pack of cookies.
It gets a lot easier though. After going in and out of keto a couple more times, it completely stops being an issue.
