The hardest part of coming clean is the first sentence. Everything after it is lighter.

All the weight sits at the start. Before you speak you are managing every possible reaction at once, which is more exhausting than the conversation turns out to be. Once it is out, there is nothing left to protect and the rest arrives almost by itself. People stall at the opening because they are imagining the worst version of a conversation that has not happened yet.

Write the first sentence down and say it to yourself once, plainly, with no build-up. Then go and say it to whoever needs to hear it, today if you can. Do not explain, excuse, or set the scene first.