What To Do

So I’m recently divorced. . We were only married 6 months but together 7 years. He had a child from a previous relationship. Our marriage shouldn’t have happened, but mainly ended because he texted me and said he was in love with his other child’s mother. So our agreement is that he has our child every other weekend during the school year and during the summer every other week. We have nothing in our agreement about dating other people except what is standard in our state that we can’t get married for 6 months after our divorce is finalized. So I found out last week from our child that he’s spending time with his other child’s mother and they are doing things together with the kids. I’m not mad that they are together I just feel disrespected. I had to hear from our child that his other child’s mother is now around my child. Me and the other child’s mom didn’t have any type of relationship. I only met her twice and everytime she was mentioned it was in a negative way. I tried being cordial even got her gifts for Christmas and Mother’s Day, but it was just really strained. I’m dating now too but I haven’t done anything with my boyfriend and child out of respect of my child’s father. But he’s not respecting me by telling me that he’s having someone around my child. She’s even spending the night when my child is there. What should I do?