My baby is 4 months old he has a lot of flem how can i get rid of it. the dr said it's not in his lungs?

Probably allergies: Phlegm is usually produced by the upper respiratory tract (nose) -- post nasal drip. If present more than two weeks it is likely allergies. Yes, even babies can be sensitive to environmental allergens (pollens, cigarette smoke, cat dander, dust mites). Clean up the environment. Use the graco nasal suction device to remove the mucous. Btw a 4 month old infant should not be getting advil.