I have just about the same thing, when I get up its a white tongue with thick mucos and saliva but it my case its from the destruction of the salivary glands, when you get up in the morning,, get a flashlight and look in your mouth, see if you can see any drainage coming from the sinuses in the back of your throat, it may look thick and white,
When iwas at the new ENT last week,, she shoved pretty hard on both paratoid glands and got nothing out of them,, I dont know what they intend to do about that
I do know every time I take antibiotics I get a black tongue which takes a week or two to clear up,, its a miserable way to live isnt it?,, You could see your GP, but dont expect him or her to know whats going on,, were just to complex for them,, and you will get referred to a ENT,, so you might as well bite the bullet and see a ent,