I brush and floss my teeth twice daily and use listerine. however, my breath is still very bad. are there any home remedies?

See dentist first: First you should see a dentist or periodontist and be evaluated for periodontal (gum) disease. You didn't say if you have had your teeth cleaned recently. Cleaning your tongue will help eliminate bad breath. If your orl health is excellent then you should look at other causes; sinus, allergies, gerd, acid reflux are the most common other causes. Your primary care may referr you to ENT

See Your Dentist: If in fact you brush and floss effectively twice daily and are still having odor issues, it is time to seek professional help. Schedule a visit with your dentist. There are other non oral related health issues that can cause mouth odor such as tonsil debris and stomach issues. Rule out any dental problems first and then be sure no other health issues are a factor. You are doing all home remedies.