Are you sure you don't have acid reflux? I had the same symptoms, and was diagnosed with acid reflux. I didn't get relief until I started a strict candida diet. For some, eliminating all carbs ends acid reflux.
Another possibility is that you have serious candida in your sinuses and throat. This can cause constant mucous. Both acid reflux and candida (the latter may be causing the former) cause excess mucous in the throat.