Why am I extremely thirsty? (I’ll explain more down below)?

Hi guys if it’s relevant then im 5’1 and im 103lbs/47kg well I was last week. I have an Eating disorder (anorexia) so I came over to my family’s house for a few days and I need to eat normally in front of them so they don’t get suspicious.
Anyway, as I have eaten now more than before I have started getting extremely thirsty, feel absolutely cold and feel dizzy also feel nauseous. I don’t understand. Nauseous is not as bad but it sometimes creeps up. I also started my period.

Is this normal?

Thank you so much for reading. Have a great day
Why am I extremely thirsty? (I’ll explain more down below)?
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