Suggest Treatment For Complete Nasal Blockage

For the last 4-5 years I've been having the same problem with my sinuses. Throughout the day they are pretty much clear and I can breathe pretty normally. As soon as I'm preparing to go to bed, and then lay down for the night, they block up completely. My nasal passages stay blocked for the entire night. If I lay in my bed any other time of the day, they stay clear though. I've tried all sorts of prescription nasal sprays, and they haven't worked. Any help would be appreciated!