Why does my new 2 mth old toy poodle eat his own faeces?

Help! I just got a new male apricot toy poodle, 2 months now. The problem is he has very watery poo, and he keeps eating his own poo after he poops. I have a super hard time cleaning his mouth and body. He makes his area where he does everything so dirty. No matter how many times i clean and wash him, he still eats his poo and make himself dirty again. Why does he do that? My other 3 dogs don't do such disgusting things. I know, the food is still undigested in his poo, but does he have to eat it? Help me with this please, i'm really gonna give up. How can i prevent him from eating his poo?