I Have a Wonderful Boyfriend, But My Ex Keeps Me Hanging On

My ex basically keeps me on a leash – he’s not my boyfriend but he contacts me almost every day, knowing that I am dating someone else.The guy I am dating now had found some of the conversations, but not the ones where my ex was basically talking trash about him.Because I kind of wanted to protect him and not hurt his feelings I didn't show him the messages. Due to my behavior (not wanting to show him the trash talk) he just ended breaking up with me.Can you help shine a light in my love life?