One side of Nose is block during sleep

Patient: I have allergy that my noses are blocked. I use steriod nasal spray which works well in day time but when I go to sleep on my left side then the left side of nose is block. After a while it becomes uncomfortable so I turn to my right side then my right side of the nose is block while the left side of nose is cleared. It sounds like there is fluid inside and shifts from side to side. What can I do to get rid of this fluid? I asked my family doctor but he did not know how to treat this problem.