mir44, can you get yourself to a lawyer asap? This sounds like abuse and parental alienation syndrome, especially since you and your son had a good bond before. Your x could be feeding his gf (and your son) lies about you too. Good counselling with a counsellor who understand abuse dynamics and how this impacts parenting/children is essential. A local DV shelter might have access to some of those resources for free. Document document document....and don't share anything with your x other than the bare minimum for your son. Try to keep all communication with him and her in writing. Record your exchanges secretly on a device if you can. A lawyer might recommend renting a house instead of an apartment just to level the playing field.