Bad breath emitted through the nose

The issue with me is Bad breath(i have had it for ever since I remember - since childhood). The unique problem i face is that the smell is emitted (not only while speaking but) even when i am 'simply breathing through my nose'. Now as days are passing, its begun to take a psychological effect: Even when anybody is 10 feet away I begin to think about my problem, start holding my breath for long periods of time, resulting in terrible stress, and consequently awful-dragon breath.
I brush twice a day(some days even thrice), regularly floss my teeth etc. Also want to inform you that I have post nasal drip. I also underwent an endoscopy & CT scan(PNS-HRCT: plain axial and coronal CT of the paranasal sinuses).Endoscopy was normal. The CT scan report (which the ENT said was normal)however mentioned (polypoidal) mucosal thikening in the sinuses, mild deviation of nasal septum to the right etc.
Other Details: when some one tells me i have bad breath, then it has always coincided with a white layer on the back of my tongue.
But if I physically exert & consequently breath hard, then I have found that others
dont complain of bad breath for those few moments.
Have this problem continuously - no specific time.
In an AC room I become more self consicious and the smell becomes very evident and very strong so I get stressed out between holding breaths.
No major diseases & have not tried homeopathy before
Sleep pattern: 8 to 9 hours at night
state of mind when i am alone & with my immediate family is composed, otherwise as described above.
Am not sensitive as such.
At no point of time ever I have been able to judge myself as having Bad breath. Its only through others(even family sometimes) Iget to know.
No tonsil stones
No antibiotics
No skin problems, some stretch marks
Last 3-4years have reduced carbohydrates intake by 50%
Yeast containing foods: once in 15 days.
Its so confusing for me to pin point the real cause. Could be sinus/post nasal drip/foods etc. Tho I like to eat onions & garlic I have decided now to stop totally eating them(even cabbage) & also to stop eating sugars, meat, eggs. Will now have more fresh veggies/fruits & tea(w/o sugar).
However I do not know whether it is from both nostrils or only one nostril.
Some relevant info may be: tried doing jal-neti(yoga exercise of allowing water to be poured in one nostril which then comes out from the other)when i poured water through the left nostril, it resulted in pain, but when I poured water through right nostril there was no pain. No intestinal problem.
Eating time is not fixed, many variations
hunger/thirst normal
Sweating is a little excessive on the head part i think.
Sleeping either on back or stomach
Sexual desires cannot be satisfied by people who suuffer this kind of problem I think bcos being in a relationship (even a friendly) itself is not possible or very difficult unless you know someone since childhood.
Am not much different but a little more pessimistic i think.
Am 26 years old male.5.9'tall,not very fair not very dark, Weight 72 kgs. Have been exercising(at home for about 40 mins) regularly for last 1 year
No major diseases in family.
I get colds and runny nose atleast twice/thrice a year
Thank you very much. I will be very grateful