Hi, I Have Had A Reoccurring Yellow Tongue For About

Hi, I have had a reoccurring yellow tongue for about a year now. When i scrape it, it goes. But everyday by the end of the day I have yellow down the sides of my tongue and sometimes at the back of it too. I've tried medicine such as Nystan prescribed to me by my doctor. I've tried other routes such as vitamin b, green tea, oil of oregano, and as of yet - nothing.