My Husband had an affair when I was pregnant with his baby...?

Hi My husband had an affair with his ex wife when I was 8 months pregnant with his child, he had been divorced for over 3 years when I met him and we dated for a while before we got married, he always went on about what a horrible person his ex was and she even tried to get him in jail a couple of times (he didnt do anything wrong but when ever she was angry she would call the cops with allegations he would be investigated and then cleared) Now she wont back off, we have our child together and his two kids from her also live with us full time and I love them, just dont know what to do...