Chronic congestion/cough in infant

I’m posting here because I don’t know what else to do! My 8 month old baby has had severe chest congestion/coughing literally for 4 months non stop. I’ve taken her to ER, pediatrician, GI doctor, urgent care, and pulmonologist. They all just keep saying because she is in day care it’s normal. But I know it’s not normal!!! She’s up all hours of the night coughing everyday. She constantly coughs up mucous. They did a culture of her mucus it came back negative and they did a chest x ray it showed severe congestion. She’s been on 3 separate antibiotics and a nebulizer for so long! Nothing is working. I have an apt with an allergist next week. I have tried different formulas etc nothing helps.

Does anyone have any insight? I’m so worried about her.