I feel so stuck need help

Okay so my 7 month old has had this congestion for almost 3 weeks now. I’m at a loss. I took him to pedi he was negative for everything and doctor said it could be allergies so we are on medicine. It seems that the medicine is not helping. We still hear and continue to suck it out throughout the day. I’m confused because it hasn’t gotten away. He is eating fine, acting fine. It just gets in the way when he tries to go to bed. We do saline drops, humidifier, and suck it out. I want to cry because I’m so frustrated idk what else to do or what it could be or if we take him in again and they tell us the same thing. Anyone else have gone through this?