I'll share what I know and ask what I can.
My longest fast was 10 days. The first time I fasted what I discovered was it was my mind telling me I was hungry, not my body. There's a pizza chain where I live called Pizza Pizza, bright orange background with white lettering. It was a 3 day fast and on the second day as I was walking that big bright sign around dinner popped up into my head, and I was like "Oh, I'll have pizza tonight for dinner." And then I realized I wasn't hungry. It taught me that we develop mental triggers, reminders, for when to eat - and that's pretty much why advertising works to manipulate us, and it does it very well; many if not most people are driven by their ego mind constantly being on and are disconnected from feeling their body properly - signals like hunger, etc. We get trained young to eat foods that don't make us feel well, and the mind then over time pulls our attention and connection to our body away from us. You may have some of this ego mind thought patterns to clear, that's telling you very strongly that you need to eat "or else you'll die" - instead of being able to relax and trust that (unless you're underweight) that your body will simply switch to energy in your fat reserves.
When fasting what happens really depends on what your diet is beforehand. If it's ketogenic then you're not also having to deal with the transition to your brain burning ketones. What's your normal diet, and do you take electrolyte supplement? Perhaps too personal however I'm curious if you take any neurotransmitter altering medications that may be preventing your brain from shifting, transitioning as easily? Feel free to email me instead matt@engn.com or just not answer that but it potentially is a factor.
It's quite common for people's sleep to get greatly disrupted for at least the first few nights which is for a few reasons. It may be disconcerting to have sleep disrupted, with potentially very vivid dreams, and transitioning into a different sleep schedule that you're not used to. One reason is inflammation level is going down in your brain, and arguably it's functioning better - inflammation has a depressant effect, so when there's a numbing or "calming" of processes.
The difficulty you mention is more likely related to withdrawal/irritability from foods you're dependant on/addicted to than the increase in adrenaline and norepinephrine that your body produces when fasting - which will make your mind faster and sharper; makes sense for this to have evolved to be a thing so if you don't have access to food and need to have a sharp mind for hunting, etc. Similarly you burn more calories when fasting than you'd burn if eating food, once again - needing more energy so you can have more energy to find your next food supply. This increased drive could make withdrawal more irritating as well.
Do you eat wheat, dairy, soy, sugars and/or carbohydrates? Wheat for some people literal acts like an opiate, so you're literally going through withdrawal. The rest of the foods I mention are highly inflammatory, and through that depressant effect people are self-medicating to "calm" or suppress their nervous system. It's possible that there's underlying emotion, unhealed/unprocessed trauma, that wants to process but perhaps you don't have the insight or skill developed yet - or it's built up past a point you can tolerate processing it, and so using food as a suppressant; this is why people consider things like MDMA and Ayahuasca ceremonies as medicines because it helps a person more easily access and process deeply suppressed emotions and trauma that was too strong to process otherwise at the time it occurred, or over time perhaps different stresses built up while ego mind suppressed/repressed and/or found different healthy or unhealthy coping mechanisms - alcohol, tobacco, certain foods, etc.
Have you tried just staying up and distracting yourself? You'll eventually fall asleep once tired. Or is it that you get too agitated and go to food and that instantly comforts you?
Here's a ~30 mins video by Dr. Jason Fung that may give you some more insights: https://www.youtube.com/watch?v=tIuj-oMN-Fk
I can potentially offer more tips and tricks once I know what your regular diet consists of.
Sorry for the delay in commenting, dang at some point rate limited how often I can post..
