I'm worried about my 14-year old son. He's always in a bad mood, hasn't been doing his homework, has been withdrawing from his friends and it's a struggle to get him to get out of bed most days. Is this normal teenage behavior, or could it be something more serious? I don't want to scare him or cause him to isolate from me even more, but I'm getting worried about him. Should I take him to a doctor?