Its possible you have a fungal infection also. This can be treated with either oral anti-fungal medication, or a rinse. In babies,it's referred to as 'thrush'. Go see your dentist and they can treat you. If they think its worse they will refer you to a specialist.
The described condition appears to be elongated filiform papilla with extrinsic stain, which is consistent with hairy tongue. Etiology of hairy tongue is not established yet. However, there are certain predispoing factors contributing to the entity. Namely, cigarette smoking, antibiotics and immunosuppressive drugs, metabolic , endocrine disturbance. Seeing an oral pathologist or oral medicine specialist is advised.