Help? please

My boyfriend confessed to cheating two weeks ago, he was sincerely sorry, and I believe him. Even though I will never forgive him, he promises to do whatever it takes to make it up to me and to prove that he wants to be with me and only me. But because we don't see each other other than weekend, I find myself always thinking about it, and I'm finding it so difficult to find trust in him again. And I'm constantly reliving what happened and it makes me sick. I love him, I want us to work out but I don't know what to do or how to stop thinking about it and it scares me so much.