Cat Won't Stop Sneezing!?

I took my cat to the vet a week ago because he was dry heaving - like trying to get a hairball up and nothing was coming. That had been going on for about a week before I took him in. They gave him an antibiotic that will last 2 weeks (so nice I don't have to give him pills...yeah!). However, this past weekend he started sneezing like non-stop it seems (probably more like 8 sneezes an hour or so) and so I took him to the vet yesterday to figure that out because he had thrown up yesterday morning. They didn't really give me any direction except gave him some electrolytes via a shot and sent me home. He still won't stop sneezing.

Does anyone have any ideas what is going on here? He doesn't appear to have any drainage from his eyes or nose but he is acting very tired and laying around alot more than usual (which maybe is a side affect of the antibiotics). I could just be worrying over nothing too :\\

Thanks so much!

Sounds like he can have a cold or a allergy.
The antibiotic will not cause sneezing.

Is there a way to treat the cold??