What's wrong with my dog?

I have a 5 year old female Chihuahua. She seems to wheeze a lot and it sounds like a cat coughing up a hairball. She also struggles to breathe often and she snores very loudly. We took her to the vet a few months ago and he didn't notice anything wrong with her except that she had a chronic ear infection, however, i am not so convinced that he was right.