Think about it...you are admitting to him that you lied and cheated. So his idea of you always being truthful to him is going to fall apart. Everything he has heard you tell him will become in question. Don't make him feel wrong to question other things. Don't be defensive of what you know on your end were truths even if he challenges them. He will take that as more indication of lies. Instead, tell him that you fully understand that knowing this may make him question other things, and that those are fair questions and that you will answer them now, and as they come up into his mind going forward. But also tell him that it's because of your understanding that this betrayal will put your truthfulness to the test that you wanted to come out clean now with the complete and unfiltered truth...so that you could start regaining his trust from the ground up. That is why telling him is so important. It means you get to start the rebuilding of trust with a bit of truth capital in the bank having told him something important that he wouldn't otherwise have known. That will give some starting assurance that allowing himself to trust you again is a real possibility.
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