15, never smoked, lung cancer?

Okay I live in a sub-rural area. Nice air quality. No family history of lung cancer (or any kind of cancer) I have had a cough in the spring and fall sometimes every year or so and this year it sounded bad so now I've seen two doctors both concluding I have allergies and that is what's causing my cough. No symptoms WHATSOEVER of Lung Cancer other than the cough (which is producing just a little bit of white phlegm) and I'm a Hypochondriac so I have convinced myself I'm gonna die. :( A week ago I was convinced I had Lung Cancer but when I started thinking I didn't I felt better, I seem to feel good when I don't think about it. I've been thinking about it again lately causing me to think I have it again. I'm almost convinced I have it but i'm going to work soon and I bet it will be taken off of my mind and I'll probably feel better. Surely I don't have it!?