Hi..
Thanks for the query..
Bad breath also known as
Halitosis can occur due to a number of causes like poor
oral hygiene, oral and dental infections,
post nasal drip, sinusitis,
acid reflux,respiratory infections, diabetes etc..
Yes, thrush in mouth can be a cause for bad smell from mouth and if your tongue is slightly coated then it needs evaluation..
You should consult an Oral Physician and get evaluated and a thorough clinical evaluation and investigations depending upon suspected cause can help in diagnosis..
The tongue coating should be scraped and viewed under microscope for confirming thrush..
As of now you should start gargling with a flavoured mouthwash twice a day..
You should chew flavoured sugar free chewing gum..
Do warm saline gargles twice a day..
Limit the intake of high aroma foods like onion and garlic..
Drink plenty of water and maintain a good oral hygiene..
Hope this helps..
Regards.