The most important thing to do is to continue to set firm limits on his touching other children. Because he so indiscriminate in his touching, I would suggest the rule for him should be NO TOUCHING (not just no touching of the genital area or buttocks). While it usually makes sense in such situations to investigate possible mistreatment, the behavior itself does not necessarily indicate that he has been mistreated. In dealing with this it is important that you stay calm and
maintain your equanimity. When you use words such as 'freaking me out' and 'freak' it indicates that you have some work to do to keep this in perspective and not become so emotional about it. It would make sense to return to the psychologist for a few sessions and see what he/she thinks at this point.