What do you think is wrong with my dog?

I took my dog to the vet about a week ago because she was shivering and coughing a little. The doctor said she had a temp and some phlegm in her throat and gave her a shot (he said it was kind of like a sinus tail for dogs) and told me if she didn't get better, bring her back and we would start antibiotics. I have an appointment in a few hours but what's your opinion on this? She does get allergies fairly often but doesn't usually cough. She was coughing all night last night so I gave her a children's benadryl (which I do occionally for allergies and approved by my vet). She stopped coughing but threw up a few hours later. I noticed too that she must have thrown up yesterday as well because I found a dried up spot on my carpet. What do you think this is? Also, she is and has always been up to date on her shots, flea treatment, and heartgard.