It's not good to drink more water than you need because this can cause electrolytes to dilute. Keeping hydrated is a balancing act. It's best to drink water when you are thirsty. Besides drinking sports drinks coconut water also has hydrating benefits and there are electrolyte replacing drinks you can buy from the chemist.
Coffee is dehydrating so if you drink coffee or other caffeinated drinks you will need to hydrate more. I also agree that eating lots of vegetables and fruits can help with dehydration. Aiming to eat 5 vegetables a day is good for you I believe, when I do eat more vegetables my skin appears less dry and more hydrated.
Of course there are various reasons a person may be dehydrated easily. A couple that come to mind are; anxiety that causes a person to urinate more often, and a condition called water diabetes.
As usual it's probably better to be safe than sorry and see a doctor.