clean the tongue

When you're brushing your teeth, brush your tounge also.

a good abrasive is a great suggestion!

second - check your diet.
Too much calcium is SOMETIMES a cause ( dont quote that exactly as it is a rarity.. but a possibility all the same )
A tongue scrapper would be a good investment if this film is the cause of bad breath, lack of taste etc. They are more effective then simple brushing.

and how am i gonna get the white stuff on the very back of my tongue. when i wanna clean it i feel like im gonna gag!!!!

When you brush you tonge, smile really big at the same time. That surpresses the gag reflex.

It really really works!

I learned that watching CSI or some other show like that.
They were in the morge with a ripe one and one of the characters was standing there smiling, when asked, that's what she said.

OH - brush the roof of your mouth and the inside of your checks too.

get a tongue scraper
it's precisely for that purpose