How did you deal with your ex's new girlfriend playing with your child?

i went to pick my 17 month old son up today from his fathers and there she was on the ground playing with my son like he was her own, i new she would of played with him before but to actually see it just hurt me so much, i mean thats my son, i brought him into the world, im the one who washes his clothes and im his mother! It just upset me that he is being 'shared'. Has anyone else felt like this? how did you get over it? How did you deal with your ex's new girlfriend playing with your child?
yep been there and now my ex's new wife and i get a long great and i know that she loves my son as much as i do but she also knows I'm his biological mother and she respects me and doesn't step on my toes. my son even calls her mom and I'm good with that because she is good to him. just be thankful that she is good to him and pays him attention. the more love he receives the more love he will give out in life! it will just take time and when you see that she is not trying to ';steal'; your son away you will be happy too. promise!