Help Please

Hey girls, idk if y'all can help me but how do you prove to your boyfriend that you are not cheating on him even tho you practically tell him every day. In the past I made a huge mistake choosing my old best friend over him and he considered that as cheating so that's why he thinking I'm cheating. Idk what to do anymore y'all, I love him so much and for him to think that I'm cheating on him when I'm not really hurts😔 Girls please help.