Skoorb, have you tried a tongue scrapper? (I know it sounds hidious, but it works)
If your teeth and gums are healthy, and you don't suffer from frequent heartburn or have diabetes, this is the most likely cause of halitosis (bad breath).
Basically, the bacteria that causes foul breath resides on the tongue far back near it's base in the throat. These are anarobic bacteria, and die when exposed to O2. They release foul gasses (sulfides) that cause bad breath.
The key is to disrupt this plaque-like layer and scrape this stuff off the tongue, removing most of the bacteria, and exposing the rest to O2.
There is also a mouthwash they sell to be used in conjuction with the scrapper. Normal, over the counter mouthwash is useless, as it doesn't penitrate the plaque on on the inaccessable parts of the tongue that cover and hide the bacteria from the air.