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I would set up an appointment with the pediatrician just to see if he is having a growth spurt and needing more food during this time. It is also possible this is emotional eating and if he might be using food as a way to soothe himself or cope with any stress he might be feeling. You can also address it with his pediatrician and possibly explore having him talk with someone. But, the first stop is the pediatrician to rule out any medical cause.
Let me know if I can support you further.