Need help on finding a cough medicine?

i need help on what medicine i should take for my nose..its totally congested..i cant breath through my nose when i lay down..only when im seated up..its horrible i cant sleep good..cuz i have to breath with my mouth and then my throat gets dry and i start coughing..and i have a headache cuz i breath thorugh my nose..please help i need a medicine to clear up my nose..