How does my doctor know its muscular pain rather than lung cancer without x-rays

[msmaincontractor]

I Have a chronic pain in my right lung, when I inhale and exhale it causes pain, sometimes at night it wakes me from my sleep when I move in bed, the pain extends into my right breast.  I saw my doctor and he felt it was a muscular pain, he said my lungs sounded fine.  That was 3 weeks ago and the pain is not getting any better, when i wake up in the morning and try to get up, the pain in my lung is very extreme and really hurts, what is causing this, my biggest fear is that it is lung cancer.

[msmaincontractor]

I went back to my Doctors surgery because the pain was still not getting better.  I was given an appointment with a different Doctor to the one I saw previous.  He decided he would send me for an x-ray, I did relay my fears to him and asked him what he thought it might be, he gave me a few different responses, pluresy, a pulled muscle. I asked him did he think it could be lung cancer and he told me there is always that possibility.  Well I had the x-ray and am waiting on the results to be sent to my GP, and now I really am terrified.  I don't know if it is stress that is now making my symptoms worse due to my fear but it really is making me lose sleep and I am like a Zombie.  I can only pray to God that it is nothing serious but thank you for replying to my question I really appreciate that xx