This is hard time but it will pass. My son and actually my daughter was the same. Around 13 or 14 things change and they are more worried about their bodies being clean. I know you think you shouldn't have to tell them to because of their age. But at 12 they are kinda like in between being a child and yet close to being a teenager. Just keep telling him and one day you will be amazed they he will take a bath everyday without being told. It is just a normal thing. Good Luck and just remember that it does sink in sooner or later.