I would go do the doctor now. I saw a surgery show on this once. The guy complained of the same thing. Turned out his insides were rotting. My mom also said this and also said that is why it is called rot gut. Of course you know that may not be what you have at all but you need to go to the doctor now~ yesterday would have been better.
I would try flossing first. If you don't floss your teeth on a regular basis it will smell like that. I had a friend who smelled like that all the time. gross.
FLoss with plain floss and smell it. It might solve the problem cheaply.
There this guy at work that his breath and body smell exactly the same as when he shits, it's so bad you can smell it 10 feet away. It's a roten smell like someone baking a **** cake in an oven. The guy wares the same pants for weeks at a time and doesn't bath and when he does bath he doesn't use deodorant and then puts the same funky clothes back on. We have told him about this and even bought him soap and deodorant but he refuses to use it and just makes excuses about stinking so bad. We have even gone to they guys parents and told them about his stench but they claim they don't smell anything. Even with this guy not bathing and not putting on clean clothes what could possably make his body odor and breath smell exactly the same as when he uses the toilet? It's like he must eat his own poop or something. the boss won't get rid of him because he says he's only at work 1 or 2 days a week and he let the guy work there because it's like his charity thing for doing a good deed or something for the church. Isn't there some kind of health service we can call to do something about him???