Pug breathing

[Rollo1]

My pug has been suffering from breathing problem since a few weeks. He has had a running nose, hard to breathe and very uncomfortable specially during the evenings. The vet has given him two rounds of antibiotics which don't seem to be really working. I personally have given himm 1ml of antihistamine( human) that seems to give him some respite. The vet did take a swap test of his snort but that was 3weeks ago but has not called me back. I am really worried because he is very uncomfortable. After every few minutes he lifts his face and threat he's through his mouth.
Please help me.