Perchance do you have autism and/or ADHD? I ask because I experience the same thing as you do, and for me, it feels like it derives from my autism/ADHD. Like, sometimes the first cue that I am severely dehydrated is that I get a headache. I get a similar thing with hunger, where I could legitimately go for multiple days without noticing I’m hungry if I don’t get reminded that food is a thing.