Can I give Dimetapp to my 2 month old baby?

My 2 month old baby girl cought a cold a few days ago and I took her to the doctor. He told me to try with saline spray and a humidifier at first. If she doesn't get better, he told me to give her Dimetapp. I started making research about it, and everyone says that it's not good to give it to an infant, and even on the label it says that I should not use for kids under 6 years of age, . My baby is coughing and has stuffed nose still and I don't want it to get worse. The doctor also told me that after I try the Dimetapp and she doesn't get better, I should give her antibiotics. I don't want to get to that!!!! What should I do??? Did anyone experience this? Please help!!! I am so desperate and frustrated...