How can I handle my ex, we brokeup about 9months ago we have still been on good talking terms, but recently?

I have a 5yr old with her, we were together for about 10yrs. Since we brokeup she we have still been acting like we were good friends. But she has been, going out with her friends who are desparate for men. Anyways I have been, hoping that we can have our family back, even though she has said no a couple of times, she has been a bit flirtatious with me. For a bout 6 of the the 10yrs we were together she has been in contact with a guy the showed her a bit of interest while she was uni. When we broke up she went cinema with in a week or so after we broke up, I then discovered that she is still in contact with him and was tell this guy personal stuff about my child. A week ago I went to her house to see my son, I noticed that her phone was going off a bit, I got curious, so when she left the room I checked it to see, I discovered that she was talking to another man and there was pictures of his face and penis, when I asked her about it she denied anything to do with him, she then said she was seeing him, and started to crying saying that now everything is going to change and how she things I will never help her again. I told her I was sorry went through her phone, and was really shocked that she had been using me. Since then she has stopped talking to me, even tho when I call to speak with my son when never picks up, or even answer any of my texts. What should I do, should stay away from her completely.