Not sure what to do...

Okay so my 4 1/2 month old has been fighting a cold for 4+ weeks. She’s been to the doctor 2 times. This second time was Monday. They gave her a steroid shot and an antihistamine to try and dry the mucus up. I’ve done everything in my power from running a cool mist humidifier, cleaning the nose out and using saline, breathing treatments every 4 hours.. it’s not going away. She’s breathing fast now, not like pulling in at the ribs just about 70-80 breaths a minute. No fever, eating normally, smiling. I’m at a loss. Idk what to do at this point. Should I take her in again for the breathing?