Orange Cause Phlegm Dry Mouth - Dehydration Because I Work Alot Inside My House?

Dry mouth - dehydration because I work alot inside my house? - orange cause phlegm

I am a computer programmer and most of my work in my house. I'm beginning to wonder whether this causes dehydration in the mouth. Is it possible or likely? As I have already in another post the back of the tongue, a whitish coating on the tongue of this kind seems to have dried or something like that. Maybe some kind of bacteria that the dry mouth? I opened my mouth, produces a large amount of mucus after drinking milk or orange juice. I'm 6'4 200 pounds and in great shape other than this problem. Ideas? Maybe I did not have enough fresh air?