Is this something else, or lung cancer?

Hello all -
I'm a 28 year old female, no prior health issues with the exception of a rhinoplasty (car accident) in 2000 and the occasional cold/flu (once every few years). I have also recently been diagnosed with panic and general anxiety disorder. Sadly, I used to smoke - on and off, for about 9 years, some times heavier than others.

Back after Thanksgiving (and right around the time I quit smoking), I developed a cough - it's slight, barely even noticeable, in addition to a tickle in my throat and some pretty intense post-nasal drip. The only thing that seems to help are allergy meds, but I have to take twice the dosage and unfortunately, end up feelink drunk. I cough, cough, cough after I eat and especially before bed. This is accompanied by mild chest pain - a "burning" feeling, but not quite heartburn, and soreness in some spots which the doctors have attributed to muscle inflammation.

I've been to see my GP three times and been to the emergency room twice. I've had two chest x-rays come back normal, as well as two EKGs and everyone says my lungs sound and look fine. But, the symptoms still persist. My bloodwork is normal. I am not tired, I have not had a fever, lost any weight or appetite, and I never cough up blood - if anything comes up at all (rarely), it's clear. I'm not having trouble breathing (except during panic attacks!!) Everyone - all my doctors, parents (both nurses), and the ER staff believe that I am experience post-nasal drip/allergies, and reffered me to an ENT. Today, at my appointment, the ENT mentioned he saw inflammation in my sinuses and throat, but nothing of concern, and set me up for allergy testing.

However, I can't shake the thought that this could be lung cancer. Should I be worried, or should I trust the doctors and move forward with the ENT route? I have been in tears for weeks over this situation. Please help me!