I read your post and some of your comments to other people and I think you two will move on from this! It just takes time. I went through something similar and asked reddit to share their experiences with getting over infidelity. One woman told me she had been with her boyfriend for 2 years when he slept with another woman. She said it took a year for her to trust him again, things were never the same, but they are still together and happy and she's glad she stayed with him. You are going to obviously need to stop talking about it with him. Or maybe make a point in your mind to have one final conversation about how this whole thing made you feel and both of you reaffirming your commitment/feelings for each other. And then let that be the final talk you two have about it. That's what I did. Forgiveness is a choice, and you'll just have to choose from now on, if you really want to be with him, to stop bringing it up in arguments. And there's no better time to have a fresh start then right at the beginning of a new year!