Thanks for your query.
Since he was previously normal and recently he has started on going for poo 4 times that means there is some problem.
Ask him if he has got pain in abdomen before stools and if yes it is infection due to parasites like amoeba in form of cyst
Other option is to get a stool routine done and it will confirm if he has any infection and you can get him treated from your GP or his Paediatrician.
Hope this answer is helpful.