There is absolutely no reason to blame yourself or think you caused this. The best thing you can do for your son is be supportive, let him know how much you love him and are willing to help him get through this. Meds typically aren't helpful in treating an eating disorder, however it really depends on if there are other issues going on (depression, anxiety).

I would find a therapist that has experience with eating disorders or you could lose a lot of time coming to that conclusion years from now.