I Have Developed Oral Black Tongue That Does Not Seem

I have developed oral black tongue that does not seem to dissapate easily or as quickly as I would like via a tongue scraper or toothbrush scrubbing of the tongue. I had an onset some years ago,with no further onset until now. I do not have,and was tested for HIV. How can I rid myself of this? In the past I have dealt with Candida.