You need to stop getting nervous, period. Bad breath is trying to let you know that something is not right with your mood(s). Do you consume stimulants--coffee, tea, chocolate, sodaa, pastries, candy bars, caffeinated energy drinks? You might be sensitive to the caffeine overload and could be chronically keyed up, i.e. jumpy and thinking too much about every moment of your life. This'll definitely make your breath and body stink. Get this stuff out of your diet and get some sleep. Slow down.
Also, you may want to try elimating all dairy products from your diet for 60 days, which is the amount of time it takes many people to clear the allergen from their bodies. It causes the sinuses to produce an acidic, glue-like mucous in the area behind that dangly thing hanging over your throat. Many, many people respond very seriously to dairy products and aren't aware of it, thinking it's dust mites or pollution or something. Your nose may not even be stuffy, and you may not have much mucous in your nostrils, but at the back of your throat it's like rubber cement and the bacteria back there are having a feast. (Legumes and potatoes also have this effect on many people.)