My 4 year old daughter has signs of separation anxiety and PAS

My ex husband has full custody of our daughter.  I have been constantly in her life since birth, until a year ago, when my new husband and I had to relocate because of work.  Since then, my ex has slowly been taking away my communication and visitation rights with my daughter, and now he has cut me off altogether.  He and his new wife have just had a baby, and my daughter is showing very bad signs of separation anxiety, i.e. crying when her dad is just in the shower.  She is being given no explanation as to why I have all of a sudden "disappeared" from her life.  It is clear from recent phone conversations that her father is speaking to her about me in a very negative way and trying to make her believe that her new stepmom is her real mom, the first signs of parent alienation syndrome.  I feel helpless at this point. My daughter is very confused by all of this.  I just want what is best for her well-being.  What can I do to help my daughter?  Doesn't she need me in her life since I am her real mother and have bonded with her since birth?

[tiredbuthappy]

of course a child needs her mother. but since dad has custody, i am wondering how much stability/consistancy you give her, and therefore how much of a role you should play. i mean no offense- you give very little to go with, and we are left to make assumptions since in most cases, custody is either joint or preference is given to the mother unless the mother is unfit. i hope these assumptions i make are wrong, and i appologize if they are.
you do not need to explain yourself, but unless you provide us with more details, i feel i cannot give proper advice. good luck.