While I'm not outright anti-porn, I do believe it is a "gateway drug" for escalating acting out.
For my husband, it was among the first steps that led down a terrible, destructive path.
It was terribly destructive to ME, as well as to him. When pornography occupies a place of such importance in a person's life, it impinges on normal, healthy sexual relationships. If it hasn't yet, it likely will.
With this in mind, I would initiate a conversation about your relationship and boundaries with him.
You don't have to have keylogger evidence to know that something is amiss. You are an intelligent woman whose husband has been absent, on some level, from the marriage due to his compulsive (or near-compulsive) pornography use.
So, saying something like, "I feel as though there's a barrier between us. I have noticed you're on the computer a lot more than usual <or any other behaviors you've noticed>. You're not as engaged in our marriage, and our sex life <describe changes you've noticed.> This hurts me. And I think it is due to increased use of pornography. When porn affects our life as a couple, it is a problem we both need to address."
He will lie. He will deny. Be prepared for that.
I wish I'd laid down the law about 20 years ago. Porn was the least of my worries, but back then it was "just porn." It escalated. If I'd known to require counseling with a CSAT, life might have been different. It might NOT have been, but it would have at least given my husband, me, and our marriage a fighting chance.
Please don't let this slide. At the very least, you need to know whether porn use is benign or symptomatic of something that is going to---or already has started to---escalate.
Addiction is easier to manage when caught and addressed early.
Millions of hugs to you.