Has your vet checked for diabetes?  The symptoms sound very much like it,
both the excessive drinking and urinating.  It is something I would ask
my vet to do if he hasn't.
 
Phyllis and the Wigglies: Generosity, Grace, and Joey (Joy)
In Loving Memory: Faith, Hope, Constance, Bandit, and Charrity
[Posted in FML issue 4599]