My cat has been not looking well.?

My cat is about 11yrs old in human years, and i have recued her and she has been abused when she was younger. And now she is acting different. She is drinking a lot of water, and is even now drinking out of the poor fishes, fish tank. And she is also misbehaving by, drinking out of the fish tank and bothering our family bird. She is also falling up and down the stairs a lot and when she jumps to go on to something she also falls off it. She also does not like to be held any more and sleeps in the oddest places, and also in the weirdest pose. If anyone knows what i should do to help her please tell me. I am taking her to the vet to see what is wrong with her with drinking all the time. but if anyone knows what i should do please tell me.