Most tea is caffeinated, and caffeine is a diuretic. It pulls water from your body, canceling out any fluids you are drinking, so you might want to consider decaffeinated tea. Same goes for coffee and some sodas.
PenelopeAnn said that 8-10 8 oz glasses of water per day are good, but you can add tea, crystal light and flavored water. DO get enough water if anything at all in your body your body needs it to function. Don't over analyze it or think about it, just grab a drink and drink on it throughout the day.
Generally, for most people, the recommendation is 8-10 8oz glasses of water. If you are dehydrated something like Gatorade would be helpful. It has electrolytes such as sodium and potassium. Also has some glucose that you need for your brain to function, carbs to burn for energy.
that isn't very much water so you probably should increase that. Also, when I got dehydrated from anorexia, my Doctor told me to eat more salt, like crackers, pretzels and broth. That will help you retain some of the the water you do get so that you aren't so dehydrated. Also, you really should see a Doctor asap.