Constant runny nose, oral mucus discharge

I have had a perennial flare-up of a constant runny nose and also mucus discharge in my throat(especially upon first waking up) which I have to expel from my mouth for a few years now. At times I suspect some of the mucus is coming up from my chest.

Some things about my diet: vegan, I avoid most sugars and prefer NuNatural Stevia, avoid non sprouted wheat, no coffee

Any ideas as to what the problem could be and how to overcome it?