if you feel thirsty - your body is saying DRINK! dehydration can make you feel terrible - nauseous, headachy, body pains, dizzy, the list goes on! sometimes poor kidney function or other problems can lead to excessive dehydration, but the simplest answer is to take in more fluids - in particular water, sports drinks w/electrolytes, juice, sprite or other carbonated products w/o caffeine, green tea, etc.
i am still holding out hope you will be feeling lots better soon. i hope you are still doing all you can to try your best as well.

oh! also! have you consulted w/ a speech/language pathologist at all? sometimes they can help you improve your swallow muscles, which can help you more easily swallow differing textures. (just an idea)

please take care!