dry mouth, watery saliva

For the past 2 years I continually have had a dry mouth, often a metallics taste on my tongue, and what little saliva I have is more like water than higher viscosity normal saliva.  This issue is causing me to spit microscopic (unseen) saliva inj all directions when I talk.  People can feel it on their face, but seem confused since they saw nothing fly out of my mouth.  It's a major embarrassment.  My dentist says my mouth looks fine, and to drink more water.  About the same time this lack of quality saliva issue started appearing I had botox shots in my forehead.  Could there be a connection?  Anyone ever experience this?