mucus menifests pattern?

Hi everyone,
It seems to me that someday I produce much more mucus than normal, then the day after that, I produce much less mucus than normal. Does anyone have a similar experience?
My pulmonologist told me that when I have less mucus out, don't think that you are getting better. I think it is good to remember that. But the fact is someday I do produce much less mucus than normal, especially when I have much more the day before. How could that be possible, since our body continuously produces mucus? I think some environmental reason might cause producing more mucus than normal, but why less than normal I don't understand. When I have less mucus out, I get nervous about it. Your experience is much appreciated.
Ling