I have a blocked nostril every night, what to do?

For about a year now, every time I go to bed at night my nose blocks (nasal congestion). I tried the aqueous nasal spray of fluticasone propionate. It cleared up, the product worked for 3 months and since then it does nothing which makes me snore like a ten wheeler and prevents me from falling asleep. It's usually just one nostril that is blocked, never the same one! Is there anything that could help me in the long run?