Do I have lung cancer?

I'm 17 years old and eleven months ago I was diagnosed with a brain tumor in the core of my brian. The tumor was removed, but that's not what I'm curious about. I've been smoking cigarettes for about a year now and a few months ago I developed a cough. It doesn't sound like anything worse than a common cold cough and I dismissed it as nothing, but it hasn't gone away. It isn't a constant cough either.. one to three times a day i'll just cough out of nowhere, sometimes there is phlegm in the cough, but I've never examined it for any signs of blood. On top of the cough, I went to a grade school for 9 years which was very very old and falling apart in some ways. Supposedly the building carried asbestos and even though the risks of that are mainly in the demolition of a building....there were holes in the walls and many patches among the piping. In the past 2 years, 3 kids (myself included) who attended the school were diagnosed with some kind of cancer. I had a brain tumor, another had lymphoma, and the last one had something in his leg. Are the coughs normal or should I be concerned? Let me know