A white tongue is generally a rough indication that you have candida. But this indication will not tell you the extent of your candida infection.
To get a better indication of whether you have serious candida issues or not, you should take this Candida Questionnaire which was devised by Dr William Crook(who wrote the famous book on candida called The Yeast Connection):
The above questionnaire works off an automatic scoring system as is geared to your symptoms and lifestyle. This test is much more accurate than the doctor's tests for candida. And its free.