...and remember, pneumonia is a very serious infection. Your son probably has post-viral fatigue. He will be tired and not himself for up to 6 months.
My 5 year old has had 4 episodes of pneumonia in the last 11 months...ALWAYS the main symptom is the pain. We took him to the ER in the first place because of the pain and not the cough, actually!
Don't worry...sounds like the pneumonia is ppresenting very low in the lung and he feels stomach pain from the base of his diaphragm the way my son did/does.
Also some kids get a lot of pain from the lymph nodes (immune system glands) at the top of the stomach when they are swollen and fighting off infection. The syndrome is called MESENTERIC ADENITIS. it oftenm presents the first time in severe infections like pneumonia and is often mistaken for appendicitis, so that's how bad the pain really is.
here's a link:
http://www.netdoctor.co.uk/ate/menshealth/206004.html
Very common....the pain will pass when your son's pneumonia is under control. Is he on Azithromax?
He could be having a reaction to his meds that they gave him for his pneumonia also. It kinda sounds like that. You need to call the pharmacy and ask them if the medicine he's on could cause stomach pain etc. You could look it up on the web also. I know alot of those meds are strong and can cause alot of stomach problems along with other things like being lethlargic. SO I would either look that up or take him back to the doctor. Hope he gets better soon.
Have you taken him to see the family doctor?
It sounds like more GI (gastro related)problem,may be something he ate ??