My Dog is depressed

by Tamara
(Texas)

I just adopted a JRT 9 months old, he's been with me about 3 weeks now, I'm worried because he doesn't like to move from a spot he found, when we go out to the park he doesn't walk at all, the only way I make him walk is if other dog comes closer, he's not eating well and sometimes when I get him out of the spot he adopted he starts trembling non stop until I carry him, what wrong with him? What could I do?