I'm in a sexless relationship, no action for 8 years or so. We have 2 DC's that came along when we were still pretending that there wasn't a problem, aged 10 and 13. But I basically gave up a long time ago now, my DH just isn't interested. I have been kidding myself for years that one day we will sort it out, when the kids are older, when DH isn't so busy at work etc etc. He admits he has a low sex drive. But no sex at all???
A friend put a seed of doubt in my mind and so I put the software that we use to monitor our children's screen time on our joint pc. And within a day it flagged porn. Looked like a tacky site where people upload images/footage of themselves for all to see. Then I noticed DH's web cam set up 
A few days later and DH appears aware that the pc has the monitoring software on it. He is very tech savvy. He doesn't know what or if I have seen anything. He would deny, deny, deny if I broached the subject. The software is removed with no drama, the pc used to be used by the kids so it's not unreasonable it was there, IYKWIM.
So, it may have been a one off stumbled across this sort of thing, or he could be a regular on the site joining in etc etc. I want to know which.
What do I do??