My Son Is 11 And This Morning He Woke Up

my son is 11 and this morning he woke up in a puddle of diarrhea and then he proceded to vomit everywhere.He has had running diarhea from his bottom 3 or 4 times today.He kept vomiting this morning until I gave him zofran odt 4mg,which was approximately at around 11:30 ,this morning.He hasnt vomited since.He has pain on the left hand side of his belly.He has often been to the doctor because of stomache pain,well before this happened.He has also been taking antibiotics Amoxicillin 875mg,of which I would give him half of the pill in the morning and half at bedtime.Cuold the antibiotics cause vomiting and diarhea?