Can’t get over the past

Okay so long story short my boyfriend cheated on me at the VERY BEGINNING of our relationship. Which was 2 1/2 years ago. I know for a fact that he has changed and he has proved to me that he is no longer that way and he grew to love me and not want to do anything to lose me. I know this for a FACT that he has changed and no longer does it. But I just can’t get over what happened. Someone please help me with tips on how to get over this and just be happy like he wants to be ):