What is wrong with my 2002 kia spectra's A/C?

My A/C had been working perfectly until yesterday that i used my defrost cause my windows were foggy. Today when i wanted to use the A/C again no cold air comes out of the vents. All the cold air comes out from the top and the bottom of the dash but nothing out of the vents. It seems as if the vents were blocked but they arent. i already tried all settings on my car but no A/C out of my vents. You hear the fan working and everything but no cold air. What is wrong with it?