How to tell my wife my problem?

Should ask this question in the relationship reboots thread - My advice is this tho.

When you explain this to your wife, tell her that you're doing NoFap as the solution. That discussion might have to include your addiction. Commit yourself to NoFap and show her that you're committed to solving this issue. If she's loving and understanding, there shouldn't be too much of a problem. You should also let her know that though she maybe upset about it, you're also upset about it too. Open communication is a great thing.