I am sorry to hear this. It is hard to know exactly what to recommend without knowing a bit more about your son's case, but I have some general thoughts.
Eating disorders are less common in boys than in girls, but they definitely do occur, and they can be more difficult to treat. It is very important to identify and treat them early, as eating disorders can be very dangerous, and people who suffer from eating disorders are also much more likely to harm themselves or to develop other psychological problems at the same time.
If you son seems still to be of normal weight and does have any other obvious symptoms other than the behaviors you have noted, you could start by taking him to see your trusted pediatrician
. They will ask some basic questions and try to get a sense of what is going on. They can also help connect you with a child psychiatrist
and other important resources.
On the other hand, if your son has any concerning look to him, such as looking emaciated, lethargic, or otherwise unwell you may want to take him for emergency medical evaluation and stabilization prior to getting more long term psychiatric help.