small white bumps on back of tongue

For three months now, I have been experiencing what seems to be very small whiteheads/pustules on the back of my tongue and whitish colored throat/mucuousy coating. There are dozens of really small pimple like bumps that concern me. I've seen three doctors about it-I've been tested for mono twice and the results were negative. I've also been tested for strep and that was negative. Initially the bumps appeared at the onset of a sore throat, but now I'm not experiencing a sore throat and the bumps are still there accompanied by bad breath. The doctors write my concern off stating that it was simply some random viral infection I recently picked up at college, but I've been experiencing sort of a metallic taste in my mouth when I wake up. The doctors definitely said it was not thrush, but I don't know what else it could be?

[scaredandshook]

I am having the same thing along with swollen papillae in the very back of my tongue. My doctor basically told me its from post-nasal drip. I don't believe it because I have had pnd on and off for years and never had this happen. I am waiting to goto my ENT appointment and I will ask him and possible get it biopsied.