Might be time for the Ear, Nose & Throat Doctor to have a look. You may have polyps or bone spurs or a deviated septum that are blocking your airway. This can make it hard not only for you to breath but also for mucus to drain. If it doesn't drain properly it can get infected making you even more miserable. If you add allergies to this mess you can get really wiped out!
Go see the doc and get some relief! Sometimes trying to fix it yourself isn't the best solution.