A very inexpensive test/possible remedy: try nasal irrigation.
Prior to going to bed, take 1 Benadryl capsule. It'll help you sleep (diphenhydramine is the same stuff they use in sleeping aids) and if allergies are getting to you...should feel better (less congested) in the morning. If you have constant mucus, it'll keep things constantly aggravated.
Worth a try.
A CT scan of your sinuses may be in order.