I'm really worried about my 2-month-old son who's been on formula milk since birth. He recently got pneumonia and was hospitalized. Sometimes, I hear crackling sounds when he breathes, and I'm concerned there might be fluid in his lungs. Could it be a lung abscess? He's generally playful and feeds well, but sometimes he breathes fast after feeding. His chest seems fine most of the time, so I'm confused. Is lung abscess something that develops after chest congestion, or can it happen without any obvious congestion?