Antibiotics can sometimes cause constipation. Probiotics is a great idea, and whatever else you usually do for your son when he gets backed up. But I really think that since he just had scarlet fever, you should take your child to your pediatrician and let him get that indigestion straight for you, plus he can doublecheck on how that scarlet fever is doing, too.
Thank you thats really helpfull , I dont know why I didnt think of constipation but now you say it think your right.
How is your son doing? Did his stomach ever heal? If so, how long did it take? I am in a similar situation. Thanks for sharing.