Help with Ex Partner

My boyfriend of 5 years had a child with a woman that he had dated for 3 months, yes, she said don't worry I'm on birth control. He owned a home, had some money, she had nothing. He had her move into the home and they for 10 years co-parented the child. Their relationship (sexual) ended when they got pregnant. She lived in MA and he in ME. I met him in ME and now we live in MA, about 15 minutes from her. She is an extremely sneaky and devious person, I could list the many things that she has done to interfere in our relationship, but the list would be too long. I continuously ask my boyfriend to not discuss any part of our life with her. I too have children, mine are in college. But my discussions with my ex are limited to the children. He does not agree and continues to provide her with any information she asks for, regardless of how personal. This only seems to open the door more for her. What should I do???