6 weeks old and congested?

My 6 week old baby is still congested. The doctors keep telling me he is fine but they never hear him cough and they don't know what he sounds like while he's drinking his bottles. I thought he was getting better but he's going down hill again. This has progressively gotten worse over 5 weeks, he now gets so congested after a bottle it sounds like he's drowning in it and waves his arms around trying to breath, last night and this morning he drank about 2 oz and while i was trying to burp him he threw up what looked like all of it, he wasn't wanting anymore after that and has just seemed really lethargic today, i have noticed phlegm in what he throws up but he's never had a fever with this so i don't know what to think, he goes to a new doctor the 20th, im doing all i can do apparently, i give him the saline drops up his nose about every 2 hours and he has his humidifier on at night, im not able to suck anything out but it does sound like its nasal congestion but after he drinks a bottle i can feel the congestion in his chest sometimes or it just sounds like he's drowning in it when he starts coughing. What else can i do?