Over it ! But need advise ladies😭😭😭😭😞😞😞😞😞

Hi, I'm 21 I married my highschool sweetheart we were in a relationship for 6 yrs but long story short I found out he was cheating on me with a 15yr old the day we got married so I the same night got my stuff and left Houston , came back and got a divorce he is still with her witch really hurts my feels but nothing I can do or the law only her mom of the girl can press charges but she doesn't want to she's allowing them to be together , so he calls me up yesterday and tells me he wants to talk so I go but one thing led to another and I was so weak and led my feelings get the best of me and had sex , now I just found out he bought a pent house and is taking her to live with him I'm so mad at my self for giving in I don't know what to do how can I get over him how can't I act like I don't care any advise please this has been killing me for a while now 😭😭😭