Sort out a physician opinion for your bad breath, if you are sure about your oral hygiene Lots of factor can cause bad breath include diabetes and lung, throat, or nose infections – for example, bronchiectasis, bronchitis, tonsillitis, and sinusitis. Smoking, diet, tongue coating are some dental issues to be addressed by dentist Hope that helps

Need professional  cleaning and polishing of your teeth .. if after that still bad breath ..then systemic condition need to rule out

A proper clinical evaluation and detailed clinical history will be required to assess any secondary factors. Otherwise the most common cause of bad breath are local factors like deposits on the teeth and tongue. Hard deposits called as calculus can cause gum inflammation and can be a reason for bad breath but they cannot be removed by toothbrushing. You will require professional teeth cleaning by a procedure called as scaling. You should increase your water intake as 2 litres is definitely insufficient, and although there is no fixed amount recommended for any age or gender, but roughly 4 to 5 litres of water should be consumed daily. Cleaning of the tongue is definitely recommended but the use of tongue scrapers should be avoided because they do more harm than good. Use only your toothbrush to clean your tongue after every time you brush your teeth. Multi vitamins are good for general Physical health but will not solve the problem of bad breath. Similarly mouthwashes can not remove the plaque and can only neutralize it, so they act as adjuncts to tooth brushing and not as replacement. Instead of over-the-counter mouthwashes, you should prefer mouthwashes containing chlorhexidine gluconate 0.2%. The type of toothpaste does not make a difference and it is the brushing technique which is important for maintaining oral health. You can ask your dentist about the best brushing technique which can be demonstrated to you on a model, or you can search for modified Bass technique on YouTube. Regards.

Some dentists do not do 'gum pocket probing' as part of their routine check up. Sometimes, gum may appear normal, but once pocket probing aka perio depth is measured, some deep pockets can be noticed. These deep pockets are the common cause of bad breath. Other than that, medical history including diabetes, acid reflux, and other gastrointestinal problem may cause bad breath.