Pissed at sons pediatrician

So my son is 3 months old. At 2 months old I took him to the doctor for his shots and he was 11.66 lbs I told them then he was not keeping much food down. They told me to bring him back if it was constant or seemed to be hurting him. A week later it was getting worse he would scream and be covered in vomit coming from his mouth and his nose. He’s been steady losing weight and his dr just didn’t take it seriously. He’s now 3 months old and 11.4 which dropped him from 27th percentile to 3rd. I’m pissed. He’s been very congested as well so he’s been to see them several times to help with congestion. Turns out he has reflux which I told them he had all the symptoms for months. He’s finally on medicine for it but he’s still not eating much and they seem to have zero concern! I want to find him a new doctor I’m just so conflicted I like one doctor in their practice and she’s only there like two days a week.