5 month old sick... wait and see? Or take to ER


My 5 month old fell ill 2 days ago with a nasty chest cold. She has ran low grade fevers. She is still drinking, peeing. We use cool mist humidifier at night. At night is when it gets bad. Her chest is so full of mucus it vibrates when breathing. Her cough is extremely wet and she Gags (and sometimes pukes) when she coughs. She cannot sleep at night bc of it and I don't know what to do. She gets some better during day and does a 180 for the worse at night. I don't know if I should take her to hospital? Would she benefit from a breathing treatment? Does she need antibiotics?