I have bad breath, and I don't understand why? No bad teeth. No sinus infections.

Bad breath. Causes. Flossing daily? Do you still have your tonsils? Debris in tonsils? Do you have reflux or heartburn? Diet? These factors can play a causal role in bad breath.
Halitosis. Is the medical term for bad breath. See your dentist for a thorough examination which may reveal periodontal disease or other unseen cause for your condition.

Related Questions

How can you tell if your sinus infection is caused by bad teeth?

Broken teeth. Severely broken down teeth can contribute to your problem if they are infected. Please see a dentist for treatment. Read more...
Need an exam. Sinusitis caused by infected teeth is not very common, but a real possibility. You need to have a comprehensive exam to determine which teeth, if any, might be involved. There is no way to tell without a professional exam and x-rays. Read more...