I'm really worried about my 16-year-old brother. He's been having this sharp pain in his chest whenever he takes a deep breath, and it's been going on for a couple of months. We initially thought it might be because of junk food, but he's actually stopped eating it for about 8 months now. I'm trying to figure out what could be causing this pain when he breathes deeply. Could it be something serious? What should we do about it?