Congested and So Scared :(?

My son is 3 1/2 months old. We went to the doctors Monday because he had this horrible cough. I was told it was viral (no medication for it). I was given a steroid for him and was instructed to give him breathing treatments. Tonight he seems so congested! I have him sleeping in his bouncy seat because I fear that if I lay him just in his crib he won't be able to breathe. Even though he is in his bouncy seat (head elevated) I am still so scared that he is too congested and might stop breathing while I am asleep. I am so exhausted since he has been sick, fellow mommy's I'm sure you understand, but I am just so scared to sleep. I'm sure he is fine and will be ok, just need some reurance :) Thanks ladies!