Thanks for Using HCM..
I read your query and it seems that your 5year old boy likely to suffer from Constipation resulting from bowel disturbance which can cause decreased appetite with no fever symptoms or vomiting..
Also Urinary tract infection
can cause abdomen pain .
Do not be worried consult a Pediatrician
and get checked for urine and stool test to diagnose earlier .
Other minimal possibilities :
1) Appendicitis (inflammation of the appendix)
2) Bowel blockage or obstruction
3) Inflammatory bowel disease
(Crohn's disease or ulcerative colitis
, caused by part of the intestine being pulled inward into itself
4) Urinary tract infections
Caffeine ,Carbonated beverages ,Citrus ,Dairy products ,Fried or greasy foods
Do not give aspirin, ibuprofen, acetaminophen (Tylenol), or similar medicines without first asking your child's health care provider.
I suggest your 5 year child to Drink plenty of water each day.
Eat small meals more often.
Make sure that meals are well-balanced and high in fiber. Eat plenty of fruits and vegetables.
Hope this information is useful for you.
Thanks & Take Care..