Post Nasal Drip - Any Ideas?

Hi, i'm 23, f, and I suffer from very unpleasant case of post nasal drip, have had it for over 6 months now. I am quite positive that it developed due to my former excessive use of cocaine as I often had sinusitis and similar minor problems. Obviously due to this condition I ceased using the drug and also had to cut down on my smoking, which are probably the only good things that came out of it.
I have tried several standard procedures, e.G. Nasal sprays, nasal wash, anti-histamines, inhaling but nothing has really made any difference.
It feels all the time there is something in my throat so I have to cough all the time as if to clear my throat, my tonsils feel weird most of the time (tho not inflamed or particularly sore, just... Weird) and I can actually feel the mucus accumulating there. When I breathe deeply I can hear weird wheezy noises coming from my throat (not chest), from around the area where the cough comes from. These noises are really the most disturbing part of it, it's a little worse when I lie down like to go to sleep and lie on my back,it feels like if something was partially in the way of breathing and because I hear this strange noise I often can't go to sleep for hours.
I was just wondering if anyone on here knows anything about this or knows of similar experience and could therefore advice or at least offer some peace of mind that this is normal for this condition.
Is there any connection with pnd and later developing throat cancer?
I have not seen an ent yet but will soon, i've been to ordinary doctors but they just prescribed me standard medicines mentioned above which failed to help so far.
Any advice or idea will be deeply appreciated!
Thanks a lot,
avine