How was he diagnosed? Did he get a culture that specifically typed it and said "hsv2"?
Did he recently - within a week or so prior to his symptoms appearing - get a Covid vaccine, likely his 2nd dose?
When you tested, did you test positive for hsv1?
I ask all these because there are a bunch of possibilities. One is that he has genital hsv1, that perhaps he got from you if you have oral hsv1 and perform oral sex on him. A lot of doctors look at patients and visually diagnose herpes, and don't actually do any testing. If he wasn't actually tested in any way, he needs to be.
Another thing we've heard a lot of is people who've had herpes for a long time with no symptoms are suddenly getting symptoms after getting the covid vaccine, especially after the 2nd dose of it. Their stories are much like yours - married people who've never transmitted it, but have had it for years. And it's possible - herpes isn't infectious all the time. Some people never transmit it.
Obviously, I don't know your husband, or your marriage, so I can't tell you if he cheated. This alone isn't near enough proof that he did.
What does this mean for your marriage? Well, if you believe that he didn't cheat, probably not much.
We don't know anything about how those who suddenly get outbreaks after covid will respond long term. Anecdotally, some are having a hard time with lots of outbreaks, others aren't. He may choose to go on Valtrex for suppression for symptoms, and to reduce transmission to you.
If it's hsv1, and you both have it, it won't change a thing. You both have it, you can't get it again and you can't reinfect him.
You should both read The Herpes Handbook, written by Terri Warren. It's free and can be read on any device - https://westoverheights.com/herpes/the-updated-herpes-handbook/
Feel free to ask me anything. Really, anything.