Supplements to help me hold water/balance electrolytes?

I developed this mysterious illness in 2020 from taking Straterra. I still don't know what it is, but my symptoms all relate to an inability to regulate my electrolytes. I struggle to maintain my vascular tone against gravity (so instant headaches if i bend over and i get very painful bulging veins in my hands and feet if i put them below my heart), i get random "hangovers" where i get suddenly and severely dehydrated for no apparent reason, my sleep has suffered tremendously, and i just pee a ton throughout the day. Also oddly enough I'm never really thirsty, and I have to be careful to not drink too much water as that will dehydrate me.

So I started taking taurine and it's been incredibly helpful for balancing my electrolytes, but it hasn't gotten me 100% of the way there. Does anyone know anything else that helps hold water/balance electrolytes in the body? I find that just drinking gatorade or pedialyte doesn't really do it, it's like there's something deeper going on and just taking in more electrolytes doesn't help. Thank you so much in advance for any thoughts. I've been to many doctors and am desperate.