Hi thanks for contacting HCM... Here your child complaining chest pain... As no specific symptoms like cough, fever etc present chest x ray done for investigation .... As she is small child there might be foreign body ingestion that can lead symptoms .... Auscultation also done .. According to cause treatment done ... If foreign body there removed through bronchoscopy if needed ... If no cause identifiable then chance of pain by muscular strain ... As your child gaining weight rapidly investigate for hypothyroidism .... Consult pediatrician for this. .. Take care ....