Been having dry mouth for a month now?

So every single time i swallow saliva, i feel like the back of my tongue is dry and sometimes the back of my tongue will have a slight yellow color. I went to the doctor a month ago and she said i have post nasal drip. I still have that dry mouth sensation and it wont go away she prescribed for me to use flonase... show more So every single time i swallow saliva, i feel like the back of my tongue is dry and sometimes the back of my tongue will have a slight yellow color. I went to the doctor a month ago and she said i have post nasal drip. I still have that dry mouth sensation and it wont go away she prescribed for me to use flonase and allegra but im not allergic to anything really. Should i go back to the doctor or should i wait it out? Could it be something else?