You may just like ice, or you may have a condition known as pica. Pica causes people to crave non-food items (although I consider ice a food item, so I've never quite understood why they classify ice-eating as a pica symptom). Learn more at en.wikipedia.org/wiki/Pica_(disorder)
It's possible it could be something called "Pica". It's the bodies craving for very unusual things, like ice, clay, chalk, non nutritional things. You could just be dehydrated. It's not good for your teeth.