Cotton mouth and dry tongue

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I'm roughly 2mos pregnant. The past few days I've been having extreme dehydration. I CANNOT get enough fluids even though I drink 2 gallons of water a day at least. I don't feel thirsty but my body feels dried out so I drink. Now I am noticing any time I eat something my tongue gets "sore" and very dry, although my mouth is in fact very (sorry I know we hate the word) moist.... Is anyone else experiencing this? What can I do to make the dry, sore sensation go away?