What must I do if I think my child needs psycho therapy?

Consult child's Dr. First with child's pediatrician or your family dr., then with a achild psychiatrist.
Find good help. There is probably nothing more precious to us than our children, so this is a serious issue. Therapists vary in skills, training and background. Finding someone with good credentials is a start, but in my experience some child therapists have that magical gift of genuineness and warmth that helps them connect with a child - you can't fake it. For more see: http://www.Childpsychotherapist.Com.