Dear Saneler, hello.
White tongue is mainly due to fungal infection
on the tongue. other probable causes are:-
1. Poor oral hygeine
5. Breathing from mouth as in some sinus
7. Some antibiotics
8. Inhalers used for asthma
treatment mainly those containing steroids
You can judge and can take prevention accordingly. You can investigate any infection of tongue by taking a srapping from your tongue, by an expert.
For your breathing problem have an Chest X Ray done.
Hope I am able to help in your query. Thanks.