Hilarious Shapeshifter

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I brought a mouse home about a week ago. I am an experienced mouse owner. The little guy has all the right toys, food, water, bedding, etc, but I noticed a couple days ago that he looks sick. His fur is dull, ruffled, and sticking out. He shakes tremendously when I pick him up, too. : (

I think that making the switch from the pet store to my home made him sick. The environments are different, after all. I am just wondering what the best way is to make him better. So far, I had chosen to not handle him for the next two days, in case handling him stresses him out more. I have also given him extra bedding and tissues in case he is cold.

Here is some extra info:

He has standard mouse food formulated for rats and mice
He has a clean water bottle with fresh water
He has organic hay bedding
He has tissues and cotton for warmth
He is very young, I'd say about one-two months.

EDIT: HE JUST NEEDED A BROTHER. GOT HIM ONE.