Try flossing after each meal. Gargle with peroxide for two minutes after using a good tongue scraper. Scrape maybe six times. Put a little salt and baking soda in a container and scoop some up on your toothbrush. Not too much salt. It's just for an abrasive. Then brush your teeth, tongue, inside of your cheeks and the roof of your mouth with baking soda. Finally, rinse with cool water then gargle with peroxide again (like mouthwash) to complete. Do this at least morning and night. ESPECIALLY AT NIGHT!! This will kill the nasty bacteria that gathers in your mouth. Stop using those over the counter tooth pastes and mouth washes. They can make it worse because of the alcohol in them. If you shower in the morning before brushing, gargle with the peroxide while doing this. The longer the better.
I know how you feel and this is what I have found to work best. I have my 8 year old tell me if my breath stinks or not. Kids are brutally honest.
OHHH! Hold your head back and stick your tongue out while you gargle so that the peroxide can reach the back of your tongue then spit. Good luck and many blessings to you. This is a painful thing to live through.