Hello! I have had the nose smell, before. I went to the ENT (Ear Nose Throat Doctor) where they stuck a camera way up my nose. I had nasal polyps, which means little growths prevent the normal draining of fluids - so the fluid would get stuck, get stinky, and that's what the source of my smell was. I had to take some antibiotics for infection but MAINLY there was two solutions to get rid of the polyps. Surgery, or nasal steroids. So we started with the nasal steroids (Flonase Fluticasone) which was prescription only back then. Luckily, it's over the counter now as people use it for allergies as well. It took a while but eventually the polyps shrunk and I am doing WAY better now. I still get issues now and then if I have a cold, so I know the polyps aren't 100% gone... but it's way way way better.
Also a sinus rinse (Neil Med Sinus Rinse) was a great way to flush out whatever is in there, it's a temporary fix but it's harmless so you can do it a lot. I don't even have to anymore because the issue is gone.
As for breath - it could be related, but it could be a separate issue? Have you been tested for Halitosis?
Another thought I had for bad breath is a) Floss twice a day and B) activated charcoal. They now have activated charcoal powders you can rub all over your teeth and mouth, (be SURE to get the kind for teeth, don't just pop open a pill, that will scrape your enamel off!) as well as charcoal toothpastes. The brand "hello" makes a nice one, you can get online or at CVS. I even have a bamboo toothbrush (from amazon) with activated charcoal bristles (heard bamboo may help bad breath as well) - not only does it help whiten your teeth, but they feel very soft, and guess what? I heard charcoal is amazing for many varieties of very bad breath, so win - win.
Don't give up, just keep trying different solutions and keep seeing different doctors. Keep a journal so every time you try a new thing, you can document what works and what doesn't. Also keep a daily log of how bad the smell is, what you ate the day before (believe it or not that affects it, like a night of beers gives me a very stuffy nose the next day).
Worse case you can try an elimination diet where you slowly remove things from your diet. Dairy, Gluten, etc to see if anything is messing with your gut and causing you to have flare ups.
I know this was a lot of info, but just don't give up!
I had the same problem. Try Myrrh powder and brush your teeth and tongue with it. Also change of diet could help. Stay away from meat and/or dairy. Look at proper food combinations such as what you can eat with starch and carbs. Stay away from alcohol!!!! and cigarettes as they tend to make it worse. DRINK LOTS of water and brush right after eating so no residue is coating the back of your tongue. I have also been chewing and sucking on black cloves, this helps. Let me know if you have any other questions or if this helped.