First, get a restraining order. Go through legal avenues and explain your worry to the court.
Magic-wise, you can do a protection spell for you and your child, and you can also do a spell to banish negative energies and people from your life. But, these won't work if you don't also take mundane steps to ensure your safety and your child's safety.
Protection ~ knot magick by witchery.wordpress.com~ http://witchery.wordpress.com/2007/05/25/knot-magic/
Tie nine knots in a cord while visualizing a protective image such as a shield or a circle of white light around you or your home. Carry the cord with you for personal protection or hang inside your home.
Simple Needs Knot
Take a cord in the appropriate colour and visualize/feel your need. Once you?ve built up as much emotion as you can, knot the cord firmly once. Keep the cord in a safe place until your need is met.
To Rid Of Troubles
Concentrate on something that is troubling you. When you are full of emotion, firmly tie a knot in the cord and then leave the room and the cord behind for awhile. Later on, after you?re relaxed and focused, go back into the room and untie the knot, releasing what has been troubling you. Visualize it disappearing.
There are three things that you may do with the cord after your need is met:
1. Burn it so that the knot may never come undone.
2. Keep it in a safe place where it won?t be disturbed.
3. Bury it in the earth.
Undo Knot Magic
Simply undo the knot. This doesn?t always work so always be sure that what you are doing follows the Wiccan Rede.