I'd start with an ENT doc. They handle noses and throats...and that includes drainage and such and might be able to put you onto something that mught clear up the breath. Have you been tested for allergies? Drainage causes bad breath-I'm married to one who has it. HE takes antihistamines and that helps. But he also can't drink milk cause it sours in his mouth and leaves a nasty odor....have you food allergies? What do you eat that causes the gas? have you kept a log that tracks the gas issues? They all tie together believe it or not. Might give you a hint. He has gas so bad some nights that the dog even moves...:D

I would think that your good old GP would be able to start the ball rolling, especially if you are on an HMO and need a referral. Otherwise I would think that a good gastro would be able to help with this..or an allergist. Bit I think that it will just take some detective work on your part to start with to find out what causes it to start with.

Good lick.