My 2 month old baby threw up a lot of mucs after feeding...he has a small cold?

My 2 month old baby does not have a fever...I took him to the dr 2 days ago. The Dr. drew blood, checked for strep and checked for a nose exam. He does not have anything but a simple small cold. The things that im worried is that my baby threw up so mucus after a feeding. Right after he threw up he was still very hungrey that he threw up a lot more mucus. Finally i let time pass like 20 mins then i fed him just a little and he did not thow up. I heard that it is good for a baby to throw up mucus to clear his chest...is that true? my baby sounds a lot better when hes breathing