Hello,
Thanks for posting your fever.
Fever along with pain in abdomen and myalgia ( leg muscle pain) can be most probably due to a viral infection like flu or dengue or any enterovirus but it can also be due to early bacterial infection which has still not shown specific signs .
Most viral infections resolve on their own without or with minimal treatment except for few complicated ones like viral hemorrhagic fevers.
Considering the age of the child it's best to get him evaluated by his paediatrician who can after thorough examination ( pulse , bp, abdominal palpation etc) confirm the nature and severity of the infection and start appropriate treatment .
Most viral fevers respond well to simple anti inflammatory analgesics like acetaminophen ( Tylenol ) thrice daily and multivitamin and zinc supplements may help in faster recovery.
So please do not worry and get an appointment with your doctor . Meanwhile you can give him analgesic as per prescription .
Hope I have answered your query.
Kindly accept my answer if you have no further queries.
Regards

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