Pneumonia requires a tremendous amount of rest while you're recovering. Don't sing; just eat healthy, drink a lot of water, and rest.
Explanation:
Have you seen a doctor about recurrent bouts of pneumonia? Because if you haven't, and you don't already have something like asthma (hell, even if you do), you should look into that because lung infections are nothing to take lightly. I had pneumonia over the winter and it knocked the stuffing out of me; it took two months before I was really feeling well again, and most of another month before I was finally not sleepy all the time anymore. And I didn't even have it as badly as I could have. Take care of yourself!