Sounds like histamine toxicity from fish
After 17 days, I don’t think you’re supposed to eat solids like that. I think 2 days of bone broth, very steamed veggies, and maybe avocado. I wouldn’t eat protein until day 3. And raw? Your asking even more of your digestion system.
When you don’t eat, your stomach acid becomes like weak tea. (An exaggeration but you get the idea). You need to slowly refeed and your digestive system rebuilds.
I do OMAD. You don’t get the incredibly rapid losses, but you also eat every day and the weight loss continues at a steady pace. I was losing about 2-3 lbs a week. You don’t take breaks to refeed. It’s just normal living and eating healthy food to fullness in a short window. Might consider it. I’ve done for 4.5 years. Lost my weight in 6 months and just love living and eating on this schedule. I’ll never do back to frequent eating. The longest EF I’ve done is 72 hours. I don’t get hungry but have headaches and difficulty sleeping - even with electrolytes. I do longer fasts only for deeper autophagy. OMAD is great for weight loss and maintenance.