My 9wk old puppy chiwhawah has dihariaha ?

Only happened 2day he seems a little sad, sleeping loads n drinking plenty not really interested I'n his food, we have only had him 4days & last night was the first night he slept alone he cried a few times but we just put him back to his bed each time, he's eating royal Canin dry food only just getting Into a eating routine as was aloud to pig out all day with his breaders, should i be worried??