Well, let me say that eliminating a bad thing so you, as a man, can grow and be more productive and be a better person and use time more wisely is all done without telling her you are quitting porn, or you have had problems with porn or you need help with porn or you feel bad about porn. !??!
My son who is on drugs has relapsed, I think, 5 times in the last 4 years! Every time he makes promises, says he wants help, etc, etc. What I wanted to see was the same thing I wanted to see in me and that was healthy habits in everyday life! I wanted his music to change (I'm reaching, I know), I wanted his room clean, him to take showers, eat right, exercise, not use profanity, go to church (anything else like, "make a commitment to Christ" is another subject), do laundry without asking, have dinner with us, hang out with good people, etc, all show me that he is not needing drugs. Whenever he lacked in these areas, it showed me that despite his promises to stay off drugs including marijuana, he was not being honest. When I was suspicious after 60 days, he tested positive.
Being off porn transfers my time to other things and I then am more healthy...minus my unemployment. Any suspicion from her is fine now that I am clean of any evidence including internet settings that I often leave alone. I even hand her my phone and she can see all I've been doing.
Again with all this, why tell her?
In the future, if she asked me if I have struggled with porn I would say yes, but I would be adamant on not volunteering the extent or the timing. It's all she needs to know. Being truthful and revealing privileged information are two entirely different things. Lying on the other hand, is bad unless of course you are protecting someone from immanent harm, which is not what we are doing here. Answering a direct question should be done truthfully or refusing to answer, as I said, "privileged information."
Now, in theory we need to ask, "is it harmful, in some way, to hold off information, such as porn use, or an affair from a wife or girlfriend/husband?"
I would say, this is like a computer question: "It depends..."