White hairy tongue can be due to multiple reasons, fungal infection called as Candidiasis is just one of them. If antifungal treatment did not improve your condition that means the cause is something else. It would be better if you consult and oral pathologist or oral medicine specialist for this. The taste buds at the back of the tongue are called as circumvallate papillae and are normally bigger in size only. That is nothing to worry about. But if the other taste buds are enlarged, they need proper evaluation. Posting a good quality picture of your tongue will be the least requirement for us to give a practically logical suggestion. Regards.