Why does your boyfriend continue to do things with his child's mother even though he is in a relationship with me?

Your boyfriend may continue to engage with his child's mother out of a sense of responsibility co-parenting requires. Maintaining a good relationship with her can help ensure a stable environment for their child. Additionally, he may feel it's important to communicate and cooperate for the sake of their child's well-being. It's essential to have an open conversation with him to understand his perspective and express your feelings about the situation.