Thanks for writing your query.
After reading your post, it seems that your child is having infection of the gastrointestinal tract and needs medical attention.
There also seems a possibility of dehydration
He should be given oral rehydrating fluids to compensate the loss of water and electrlytes.
He also needs a probiotic
preparation alongwith antibiotic and antiamoebic to treat the infection.
If he is not taking orally, he should be taken to the ER to give the medicines in injection form.
Give him light meals prepared in hygeinic conditions.
I hope this is helpful to you.