my 2 yo son is obsessed with drinking. He must easily drink 8/10 cups of juice or milk a day and goes absolutely mad for it, so I have to give him it. He downs every cup I give him like he is so thirsty and is constantly whinging "juice juice". How much fluid is really needed? His nappies are always soaking wet after 2 hrs and there is no way I could even start potty training him, he wees all the time. Any advice?