DNS, Have Foul Smells From Nose And Mouth, No Changes With Treatment, Excellent Dental Hygiene. What Could The Cause Be?

i have been suffering from bad smells emitted from my nose and mouth for a number of years. Even when my mouth is closed i can smell the bad smell and it has a fecal odour to it. I drink lots of water and have taken antibiotics , and then probiotics for this in the past, but this seems to have little effect in helping my issue. my tonsils have gaps in them (crypts) and if i gently put a cotton bud in one of them and then take it out and smell it i smells terrible. im sure this is where the smell is originating from. whenever i sneeze there is a different mouldy smell in the air afterwards. i didnt practice good oral hygeine as a child and as a result have two fillings and a root canal , but ive always brused twice a day and flossed/ mouthwash since before the problem started. i also have a deviated septum and part of my nose has been worn away a bit from sniffing things - better to be honest about the issue - also when i have sniffed things the snot in my nose the next day is yellow and stinks. my nose has been broken numerous times as well but never been fixed at a hospital, im not sure if this makes a difference or not. can you shed any light on what you think the problem might be please?