What causes recurrent pneumonia?

Question: My name is XXXXXXX I have an auto-immune condition called masto-cytosis, which is rare. Although I was once extremely healthy, the past 20 years my health seems increasingly less resistant to disease. I am currently 64. In May of 2015 I went through a multi-months long period of severe fatigue. 4 months later I developed a cough, and could barely breathe. I was diagnosed with sever pneumonia. Several rounds of medication finally seemed to resolve 99% of it, as I was still extremely tired. It reoccurred again last December, so I again was on multiple rounds of medication, the last being Levoflexin (or something like that). This past month I again developed pneumonia and was quickly prescribed Levoflexin again. After 10 days it resolved probably 95%. A second script was added which I took for another 2 days, but am wary to take any longer because my liver was previously damaged, and today I have problems thinking talking walking lifting; my arm and leg muscles have been in terrible pain. I have asked my doctor about this, and she tends to brush it off, so was wondering if this is natural and how long it may take this time to get back to good health. Also how do I avoid getting pneumonia? I work in a lab in downtown XXXXXXX