Feeing used

I’ve recently broke up with a guy that I thought I was gonna be with. He seemed to be a great guy I just don’t understand why he would completely flip and just do me so dirty. We would talk about life our fears what we wanted to be, going back to school. I felt completely comfortable with him. Mind you I have a 6 year old that I never introduced to anyone and he met her. He actually initiated the hole thing that he wanted to take this thing further. So he met my daughter (dinner setting and a walk) she didn’t seem uncomfortable she was asking him questions he responded but he seemed uncomfortable. Any ways over time I’ve get he was getting distant he wouldn’t call as much blamed it on work and when I asked him what’s was his deal he said that he needs to concentrate on what he has going on that he needed time to figure things out. I was taken a back from that response because he met my daughter he knew what I was looking for in a partner. Well weeks go by and I find out that he has a whole new girlfriend that he is living with I’m just in shock and I hate myself for introducing him to my kid any advice