Sorry divorced coparenting

I’m so so sorry for saying this but i have to . I’m so recently divorced of my husband and we were together 9 years and sorry he started dating someone for the last 6 months (dating prior to our divorce clearly ) . Anyways I am the bitch for saying this but I can’t hold it In anymore right now . I can’t be happy go lucky right now with everything . I will be “happy” for my ex husband but it’s not real . I don’t believe he will ever change honestly . He will be the same person and will only think about himself . And how do I coparent with someone who seems nothing wrong with anything . Ever .