Pregnancy post nasal drip

Momma of 4
Help! For weeks I get post nasal drip so bad that I gag, so constant sometimes that I almost vomit. I've tried Claritin, vaporub, gargling, I bought 2 UV light filters, vacuum 2x a week, change the a/c filter every 2 weeks....what else can I do? It keeps me and my husband awake from the coughing.