I have been fasting for years on and off and in December 2022 I started for the first time cycling consistently every morning about 20 to 25KM and I went through something very similar.
Since I always believe that it takes 2 weeks for things to hold and adjust, what I did was scale down my fasting from 22 - 26 hours to about 16 - 18 hours max, I increased my protein and carbs a little, and gave in to my sweet tooth (dark chocolate and the occasional egg tart were my cravings) during my fasting window - delay don’t deny. I did this for 2 weeks and I even skipped a day or two but kept the work out and other activities like long walks.
After two weeks, once I felt my body got used to the activities, I went back to a fixed 20:4 or more. Pumped in some extra electrolytes in and out of the window on the first few days. And so far, all the “symptoms” are gone.
Even recently, I fell sick for a week and was worried that I would struggle to get back to that routine but it was okay I am just making sure to take in enough protein and a bit of extra carbs especially if I’m doing more cardio.
I didn’t see your diet plan in the post but it sounds a bit like not enough calories (or a type of food group) and maybe lacking in electrolytes or even a bit of dehydration.
My advice: Don’t give up, scale down the fasting first for 2 weeks, tweak your diet, maybe keep a journal to track.
P.S. Craving is gone now so kids are eating up the dark chocolate.
Cravings can be a result of vitamin or mineral deficiencies or certain gut flora demanding sugars, the mechanism of which is still poorly understood. Don’t try to drop weight too fast, giving your body some fuel when you burn calories is good, specially after being sick for a while.