parental alienation what do I do

My son has been kept from me since 2007. His mother constantly moved him from place to place after our divorce to keep me from having a relationship. Everytime I would find him she would move again. I finally was able to track her down the last time and quickly filed a contempt of court against her. We were given temporary orders of step up visitation. The first few my son was terrified to be around me and she was constantly late bringing him. Then he finally started loosing up and having fun. We were to start overnight visits per step up order and when I arrived to pick him up I waited 15 mins before he finally came outside and looked terrified like I was some kind of lunatic and said "I don't want to go II'm not comfortable" I asked him what happened why is he scared he just put his head down and his mom came outside and whispered things to him then he said again "I don't feel comfortable" & he started crying then went inside. Our temporary order requires 80% compliance. Alienation