Thin, yellow coating on tongue?

For the past few months I have been dealing with a thin, yellow coating on my tongue. It begins in front of the circumvallate papilla and continues forward on the top-sides of the tongue (but not the actual sides of the tongue nor the middle of it either). Whenever I brush my teeth and tongue, it comes off easily with no pain nor bleeding. I hardly ever consume foods with yellow dyes in them.

Besides the yellow coating, my tongue has a normal color to it and appears fine; no pain, no swelling, no cracks, no large bump, no blisters, no bad breath, etc.

I've read on various sites that it can be attributed to many things ranging from dehydration to HIV... so I'm at a total loss yet freaked out. I've been recently tested for SDIs/STDs and am NEG across the board.

What is likely causing this?

[healthfreak007]

*** forgot to add that I am not a smoker.

[Linda355]

It is more than likely a bit of a fungal infection, go to your doctor or dentist and have them check it out.  If that is what it is then a simple one time pill will take care of it.  If you use a lot of bacterial killing mouthwash and toothpaste you could have disturbed the ph and bacteria balance in your mouth.  Also antibiotics can cause this.   Eat yogurt , that helps also.