Hi there welcome to the BB and BO club everyone here has BB, BO or in extreme cases both which as you say affect our social life drastically. You sound like you definitely have something call post nasal drips where mucus runs down to the back of the throat rather that out the nose, when this mucus site there over a period of time it rot and gives of that offensive smell. This is very annoying some old home remedies for the this is Warm salt water.
If you have any old nasal spray bottle fill it with salt water and spray into the nostril 3-4X 3X a day.
gaggle your mouth with some warm salt water often as well cut down on your milk intake as this contributes to the white or yellow build up and finally drink lots and lots of fluids water is your best friend. when you brush your teeth you have to somehow scrub that out without damaging your tongue some people suggest tongue scrappers but the tooth brush works just fine.