Googled what you typed and came back with this yahoo answer
"The tongue is normally covered by hundreds of tiny bumps known as papillae. Sometimes these papillae become enlarged, allowing bacteria to hide within the recesses of the swollen bumps. The bacteria that take up residence in the papillae produce porphyrins, natural pigmented chemicals that can turn the tongue colors ranging from yellow to black. This can cause the tongue to take on an overall yellow discoloration.
Although this is the most common cause of a yellow tongue, occasionally a more serious health problem such as jaundice can cause the tongue to turn yellow. Jaundice can indicate an undiagnosed liver or blood problem that needs immediate medical attention. Another possibility is the presence of oral thrush, although this usually gives a white tongue coating, rather than a yellow tongue appearance. For this reason, a yellow tongue may need to be evaluated by your doctor if it fails to resolve.
What steps can you take to treat a yellow tongue? Because this condition is usually caused by enlarged papillae, efforts should be made to reduce the swelling of the tongue papillae. If you smoke cigarettes, try to limit the number you smoke since this can further irritate the tongue. Dehydration is another factor that can make a yellow tongue worse. Drink a glass of water every hour and eliminate coffee and other sources of caffeine from your diet which can further dry out the mouth and increase bacterial growth. Some medications such as antihistamines and antidepressants also dry out the mouth and can make a yellow tongue worse. Ask your doctor if the medications you're taking could be contributing to the problem.
The good news is that a yellow tongue caused by enlargement of the tongue papillae is benign. Sometimes it helps to reduce the yellow pigment by brushing the tongue lightly with a soft toothbrush to remove excess cells that can harbor pigment producing bacteria. Follow up by rinsing the mouth thoroughly. Repeat this several times a day. If the symptoms persist, see your doctor."
I would recommend going to see a doctor..
One can drive himself to madness in the obsessing goal of reason, without the knowledge of love and laughter.