What can cause REALLY BAD breath aside from a germy mouth?

bad breath
jade asked:

Okay, so my breath really stinks sometimes, and it’s not because i haven’t brushed… i always brush my teeth, tongue, the works. I do have my tonsils but they look pink, not white or bumpy. I don’t smoke, i don’t eat garlic or onions. It stinks so bad that people can smell it even with my mouth closed apparently the air that comes out of my nostrils smells too.
I think it’s something in my stomach, cause it does feel a little acid sometimes, but at others i don’t even feel it and people tell me i smell! Also, i don’t stink all the time. I don’t have rotten teeth or cavities. What could be causing this? What can i do to get rid of it?

Rapid Cure for Bad Breath