You'll need to change your diet. The poster above me had the right advice. Green veggies and increasing stomach acid is key. If the odor is that fowl there is a high chance you have food rotting in your system, which is caused by low stomach acid. Be careful and only supplement when you eat though.
Anyways, try out a diet consisting only of lean meat, seafood, and green veggies. Drink tons of water. The smell should go away. If it doesn't, see a doctor, your organs might be in trouble. If the doctor doesn't help, see a chinese traditional medicine practitioner; either that or a naturopath. They do well with Body Odor issues as it's usually all connected to the digestive system. If your diet is high in sugars and starches, you have your answer as to why your breath smells. This is something you'll have to stick to all your life, there will never be a miracle herb or pill, you must change your diet and be gentle on your digestive system for the rest of your life.
Do you notice your breath getting worse after eating certain foods? If so, which kind?