I have a shih tzu yorkie mix and she is 5lbs. She is eating fine and her bowel movements are normal. She likes to be held or on my bed. Lately she has been mopey and seems depressed. She will hide under my bed or scratch the side of my bed at night until I pick her up. She does have a weak tummy at times. Not sure what is wrong with her?

When you say "lately" - how long has the changed behavior been going on?

If she has a tender tummy, then maybe she doesn't feel good? Just because she is eating and pooping without any issues doesn't mean that there might not be something wrong.

Has there been any recent changes in your life? Dogs are very sensitive to changes and will act different.. especially if your mood is reflecting sad and wanting to just cuddle.

Is she new to your family? Sometimes if the dog is new, you won't see the real them for a few weeks up to a few months.

There are over a hundred different reasons your dog could be blue. If you can't think of anything that changed in your life within the last couple of days/weeks/months, maybe a trip to the vet for a health check.

3days

I would be concerned. Call the Vet and ask - maybe something scared the dog; maybe the dog is sick. No one to know without actually asking a Vet.

Three days would be enough to concern me.