It sounds like your
plant is shot.
Jades are usually very easy
plants to grow, with hardly any common problems. With one exception, that being mealy bugs, and it is very easy to tell if you have a infestation of them, as they look like little white tufts of cotton. Providing you are giving it indirect sunlight, and as long as you don't have it in a drafty area, and you let it dry between waterings, they usually do very well. Yours may have been damaged when you brought it home.
However you can take some of the leaves and start new
plants. All you need to do is take the leaf and place it face up, on a bed of semi moist potting soil, give it some good light, and within a week or so you should see some new growth appearing from the stem area. they are one of the easiest
plants to propagate from leaf cuttings. Hope this helps.
Mike