Suggest An Antihistamine To Reduce Mucus In Throat

I have two problems, one is getting out of breath. I take symbicort & a nasonex, the symbicort does help me very much., but the nasonex doesn't seem to do anything.
Secondly I have what I believe is a sinus drainage in my throat I have thick mucas back in my throat so I am always clearing my throat it also sometimes makes me cough. I read an article that says a saline nasal spray may be useful for flushing the nasal passages & throat. I have not tried this yet. Also suggests an antihistamine to reduce mucus. What do you think? Thanks, Adele Poirier