ive nearly overcome a similar problem. You need a netti pot or a sinus irrigation machine (which i use). Fill with water and add fine Sea Salt (about 5 grams). To this you then need to add 15 drops of Grapefruit seed extract.
The irrigation machine and the netti pot both flush your sinuses with this liquid and kill any infection. I do this both first thing in morning and last thing at night before brushing.
Ive been doing this for 3 weeks now and im allready mostly bad breath free, it should be another few weeks before im totaly clear.
This infection is likly to have collected in your throat aswell so drink 12 drops of grapfruit seed extract with a glass of water 3 times a day. I used to have a lump in my troat which was all this bad mucus, this has now cleared up. 1 bottle of Grapefruit-Seed-Extract lasts over a month and is fairly cheap.