@WGC3
I know you were being lighthearted with your OP, but your situation is very much not lighthearted.
There is some very bad advice on this thread (still reeling from the idea that someone would become pregnant, "lol", as revenge on an errant spouse).
FWIW, and in response to PPs' suggestions, you can't change the locks unless you are the sole owner of your home. Plus 'evidence' is irrelevant if you end up divorcing. The law wouldn't give a toss if your DH had been molesting children. The law is interested only in what is best for any children of a marriage. Even if you had no 'evidence' of infidelity, what he has done thus far, even if he doesn't shag the OW, could be categorised as 'unreasonable behaviour', should it get to that point. You don't have to go into detail on a petition.
Now a different perspective (and have NC for this, obviously).
I had a very longstanding EA when I was married. By the time XH and I separated, the OM was the only man in my life. We never had sex while XH and I were still living in the same house. This (and I am being very honest under cover of anonymity here) is because OM never offered it at that stage. If he had, I would have bitten his hand off. I used to fantasise about working with him and going away on a work trip that ended up with us sleeping together. Or even just kissing. Anything at all.
XH knew that I had feelings for my EA, but never really said anything beyond barbed comments.
The difference between our situations - and it's a big one - is that I had come to loathe XH because of his behaviour towards our children. There was no way on Earth that I was going to go near anyone who could do that.
Leaving that aside (which did play a big role)... thinking now about how XH handled my EA, I think he did the wrong thing.
He should have done is put his cards on the table and say that he knew that I had feelings for EA, and that he wasn't willing to live like that any more. He should have asked me to cut off all contact with EA so that we could work on our marriage.
As it was, he just sniped at me about EA. If he had done as I mentioned above, I would have been scared, but would perhaps have been grateful to him for getting it out into the open, and we could have had an honest conversation about what had gone wrong.
I think it can be very hard to come back from this sort of thing - but I don't think it's impossible, if there's no other impediment. In my case, there was a massive impediment, in the form of XH's behaviour towards the DC, which propelled me to the EA. In your case, though, it doesn't seem that there is any major thing driving the EA.
That being the case, try being honest with your DH. If it ends up with him telling you he no longer loves you and wants to end the marriage, that's horrendous. But arguably less horrendous than being kept in uncertainty.
Sorry for the essay.