Whats wrong with my dog? How can I help him?

I have a Tea-cup Yorkie (5.4lbs) that's turning 5 in November. We went on vacation and left him at a doggy boarding thing. When we got him back he was coughing,sneezing, and he couldn't breathe because he was so congested. We took him to the vet and they said he has an upper respiratory infection. They gave us medication and said he would be much better in the next 48 hours. But its Friday and it seems like it got worse. Hes always up at night sneezing or coughing ( he dosent cough up blood though) Im very worried for him. Any advice? Please be serious i love him so much. I hate seeing him through his suffering, sometimes i get a couple tears because he cant breathe. Please help me.