My Shih Tzu is 1 1/2 yrs.old...I've had her for for 6 wks. I'm told she was on dry dog food, but from day-one, she has refused it, plus all the brands I've bought; and only wanted our food, so we gave in... For the last wk her stools have softened into a now loose stage and she is sluggish and lost her appetite... I made the mistake of giving her worm med on an empty stomach(wont do that no more). It came up an hour later.
Your pet should be seen by a vet. It really sounds like she is not feeling well and I do not like the fact that she lost weight. Vetcare