DS2 was exactly the same big fat and unsettle all the time, it drove me completely bonkers. I even went to the extreme of putting him on formula only to have to step back and relactate because that wasn't the issue. I got him tested for diabetes and all because he was just thirsty all the time and even now at 2.5yrs he still drinks what ever it be cows milk or water like there's no tomorrow so i have just put it down to him being a big drinker... guess some kids are just like that.