blastocystis to a child - needs help

my son have blastocystis, he is 2 years age, we took a stool to test because he is cryng a lot and say he have a stomach ache
he also cries hystericly every time he feels that he have excrement
the doctor told me to give him an Antibiotic treatment
i prefer a natural treatment but don"t know what to do and if it can be done for a child his age
do i need to do the treatment to all the family?