What could these symptoms mean?

Hey guys, I am hoping someone can lend some light on this problem of mine.  I am a 24 year old male, smoker for 10 years, and within the past week work has been getting very stressful. I drink alot of pop, smoke alot of cigarettes, but that is about it.  

I have been having a dull, achy pain in my chest, and I cannot tell if it is the pectoral muscles, my heart, or my lungs. If I have a cigarette it seems to show up, however when I lay down to go to bed, I feel it there as well, and suddenly become aware of my heartbeat moreso than any other time during the day.

I have not had any health problems relating to that. I asked a few buddies at work and their automatic reactions were lung cancer. That scares me very much because I do not have health insurance.  

Has anyone had a dull achy pain in the chest? It is not stabbing or sharp, more a cool feeling across the chest, or the lungs, cannot make sure for certain.

Thanks in advance for the help!

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Any help able to offered here?