3 month old with constant stuffy nose & phlegm?

My baby has been congested and had phlegm for over a month already. i advised the dr about her phlegm and said its fine as long as she doesnt have a cold. left msg with dr to tell me how to get rid of it but hasnt returned my call. i can hear/feel the phlegm when holding/burping my baby. there have been a few times where it seems like shes going to cough it out but doesnt. what can i do? please help. shes also thrown up because of it too