Coated white tongue...what is this?

For about an year now, I have had a tongue that has a white coating

It covers most of the area of the tongue, and brushing/scraping doesn't remove it completely and after 1-2 days reappears

I keep good care of my mouth, but I am not sure if this is a sign of digestion instead?

It is very distressing for me as it gives me very bad breath

So is it bacteria, fungus, or something else?

I want to get it tested, but I don't know how - do I do a mouth swab or blood test? and where can I do this? Tweet