You are more than likely malnourishing yourself and not getting the energy you need. When you’re doing something as extreme as 20:4 it’s paramount that everything you eat has the right amount of protein, vitamins, etc. so that your body can function properly.
Sounds to me like you are suffering from an onset of Rabbit Starvation / Protein Poisoning.
(Side note, all you ever heard about protein - none of it is true. It is all part of a massive scam to sell a cheap dairy industry byproduct off at a high mark-up. The amount of protein it takes to build a days worth of muscle growth is in the MILLIGRAMS region.)
Many of the best foods for human consumption, happen to also be rich in protein, so don’t get me wrong here. Just understand that protein itself is very far from what it was cranked up to be. And in case of protein poisoning, it could literally kill you, if you kept eating ‘clean’ for long enough.