I guess it was about 3 years ago, I was staying out here, and at the time we only had the little cabin. 10'x10' log cabin, no water, heat, or electric, and it was a brutally cold winter. But, we had animals out here to take care of, the wife and kids were staying with her Daughter... and I really didn't want to stay at my Step Daughters place with her family. After a while, I started getting sick, much like you, I thought it was Pneumonia. In years past, a trip to the farm store and several injections of Penicillin later, I'd be good to go.
Not this time. In fact, it got worse and I lost my voice. I went from being heard 1/2 mile away, to not being heard 3' away. Doctors were clueless. Long story short, I found one Doc who had a hunch, and a Pet scan confirmed it- A mass in my left lung. My wife was able to to get me in at the Cancer Treatment Center in Tulsa, where I started chemo and radiation. And all that time, I figured if I had cancer, it would be where I was having sharp pain near my temple. After a few months of complaining about that, they did indeed find a small tumor there as well.
After a total of 3 months chemo and radiation, I developed super powers, and can now turn into a huge green monster when angered... well, maybe not. But, I am still alive, and so far, still clean. So, Like Sir Charles said, don't wait too long. And I hope Sir, that you have a good diagnosis.