help! my son can't breathe at night!

Help me!! For the last 2 nights. My 11 week old son has develop a cough and stuffy nose. So I thought he was getting a cold. Which I'm sure he is. I have been checking his temp and it's normal. He eats fine. Just those 2 things. Coughing up mucus and a real bad stuffy nose. You can hear it up his nose and in his throat.  But at night time, it gets so bad to where he wake up screaming cuz he can't breathe so I immediately suck the stuff out plus use the "little remedies" saline drop. He scaring me cuz he struggling to breathe. He will be 3 months on Wednesday. I'm gonna call the dr again today cuz the first time they told me to use the drops but it's like he cavy cold getting worse. What can I do to help him breathe better? And ease the cough