Are you on lithium? Have you had your blood tested regularly?

I was just diagnosed with 'diabetes insipidus' which was directly caused by lithium. It is a kidney condition. It is characterized by peeing a lot (which appears diluted). You will feel dehydrated more often than usual too, feeling the need to hydrate frequently. The condition cannot be reversed however the treatment is basically drinking a lot of water. Unfortunately, there is nothing you can do about the active bladder.