Given your previous rough sleep schedule and overall stress, it doesnt sound off. Caffeine withdrawals tend to stop after 48-96 hours but maybe youre still withdrawing if you had a looooong established habit.
Or, to be honest, what I swear happens is people used to intense stress have constant cortisol and anti-inflammatory going on. It keeps you up and operating, and then as soon as you start having a relaxing or less stressed time - bam, instantly sick. But they were already sick (like a flu or whatever) just pushing through with constant adrenaline and cortisol. I dunno, nausea, fatigue, headache is pretty wide constellation. If its really getting to you in a few days, maybe try a doc. Otherwise, keep eating well, hydrate (HYDRATE), take some advil and keep up your sleep schedule change.
