Sinus drainage also makes you cough, a la post nasal drip, especially when you lie down. Unfortunately, allergies frequently lead to upper respiratory infections, which worsen the post nasal drip and give you a really nasty taste in your mouth and a bad smell. One indication that it's allergy related and not conventional bronchitis is that your discharge is clear and colorless, not cloudy and green or yellow. And constantly swallowing phlegm makes you really nauseous. Sorry to be graphic, but that's the reality.

Allergies also commonly develop and worsen as we get older, so not having a reaction the year before doesn't mean you're not allergic now. If you don't want to visit a doctor, you can try an over the counter allergy pill along with an OTC nasal allergy spray. Some people find relief with plain saline nasal spray. It would probably be best, though, to get tested to see what, if anything, you're allergic to, so any medication can target them appropriately. It's a pain in the neck, but it can really improve your quality of life.