My 6 wk old baby has been congested for a couple of weeks and spits up most of his feedings. Please. Help!?

He had brocholitis a few weeks ago but he is fine from that now. Since then he has been congested on and off. He spits up most of his feedings. Doc said he was fine but i am still not convinced. When i put the bottle in his mouth to feed he gags... it is very frustrating! What could be causing this congestion?? I've tried everything and nothing helps (saline, humidifier, sleeping in car seat) HELP!