I cheated on my boyfriend and now he doesn't trust me?

I don't know what to do. .we are still together and i am not going into details about the situation. you don't need to tell me how Wong i am because i already know. i just want to know how to get his trust back. we live 30 min away from each other and when we are together we are fin. but when we are apart, he never seems to let go of what happened and he suspects that im gonna do it again. please help me!!!