Why do I have bad breath even after brushing my teeth?

Lately, not long after brushing my teeth
I often feel like my mouth tastes dry and sticky.

I tend to brush my teeth quite thoroughly.
I'm also using a tongue cleaner, but I don't really notice much of a difference.

Could the bad breath be caused by cavities or gum problems?
Or I find myself wondering if the stomach or tonsils could also be the cause.

For those of you who have visited the dentist because of bad breath, did you find the cause right away?