Hi,
To start, its pretty common to have 8 year olds be choosy eaters. but lets work on that. It is important for a child to be strong in uncomfortable situations and control the symptoms rather than being swayed by the situation, for that, lets start working on the strengthening the mind and be able to process the situation. You can actually start by some mindfulness exercises with him, like chanting, or block colouring, or simple guided meditations. That will help him to relax in those situations when they arise.
Have you got him dewormed? well, its fairly common for young children to contract worms while playing, so a periodic deworming is good enough. You can repeat that every 6 months till 12 years of age.
Dose: T.
Albendazole 400 mg in the night as a single dose. That should definitely help you.That will also increase his appetite and such stomach upsets. I would also recommend you to start a
probiotic, it can be any product that's available in the market available at mother dairy, Yakult etc.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Gaurav Nigam, Pediatrician