I have a very distinct "mothball" smell in my mouth. It's not even like when I'm right in her face about to maul her. She says she can smell it when we are in the car together.
This could be a sign of h.pylori.......you should probably check w/your gastroenterologist for some tests. This sounds very digestion-related to me.
Also, get a urinalysis done if you have not had one in a while.
(There are some very distinct illnesses that cause mothball breath, and you would be better served to consult with a doctor, rather than an internet forum, to find this out. I know i would.)
I dunno why people always thinking mouth when they have breath smells.

Stomach / gut is often the culprit. Good luck!
But please, do take my advice. When your body starts to develop distinct smells, it is often a sign of something internal....breath, skin, pores, etc. are all just outlets for the internal body.