Oral thrush?

White coating on your tongue is caused due to bacterial infection by a buildup of bacteria, debris, fungus, and dead cells. This can be treated with
1)antifungal medicines such as clotrimazole lozenge, itraconazole
2)nystatin, which is an antifungal mouthwash that you swish around in your mouth and then swallow
But before implementing all these you must concern with your nearby dentist at least once.

White coating on the top of the tongue, very common. The bacteria that grow there produce sulfur containing compounds that are usually white in color and also smell. That is bad breath. To get rid of the white coating you need a tongue cleaner that has both a brush and a scraper.