How to get rid of constant nasal congestion?

I am constantly congested in my nose and sinuses. Half the time I can breathe through one nostril and it alternates between left and right but I mostly have to breathe through my mouth. When I sleep I wake up throughout the night because breathing through my mouth makes my throat dry and sore. I constantly feel like I need to swallow and when I blow my nose I just end hurting my ears because nothing comes out. I have seasonal allergies but the problem still exists when I take medicine for the allergies. I've tried a neti pot and over the counter sinus spray and they both work temporarily, maybe 2 or 3 hours. What could be the problem and what else could I do for it?