Yes, been through the exact same thing. This was back in 2004. We had been married for 14 years (together for 17), and had 2 kids aged 7 & 5. We had just bought our dream home, and finally thought we'd made it. Nothing wrong in the relationship, still had date nights and sex etc. But I found out that he'd been messaging other women, and kissing them too. I'm pretty sure he had sex with someone else, but I have no proof.
I decided to forgive, for the sake of our family unit, the kids etc. He just carried on, but got better at hiding it. Cue 3 years of absolute hell, with him doing this, and me turning detective.
Then, in 2007, I was in a nightclub, and got chatting to a guy, and out of nowhere he swooped in and kissed me. It was like a light bulb moment, where I suddenly realised "other men are available". That was the first indiscretion on my part, in the whole 20 years we had been together. I knew then that I was worth more than this. I made an exit plan, and I'm not ashamed to say that in that year that I was lining up my ducks, I also had some dalliances with OM.
By 2008, I had sorted everything out for our split, and let me tell you, he was MORTIFIED. Well, tough shit. He begged me on his hands and knees not to go. And bizarrely, that was the first time that he really understood the ramifications of what he had done. Before, when I was still playing happy families, he just didn't see any reason for him not to have his cake and eat it too. So, once he knew we were over, he decided to romance my very best friend and shag her. So, I lost her too at this point.
I moved out, and bought myself a lovely little house, and I was free of all the lies and bullshit. I joined a few dating sites, and luckily I met DH, just 8 weeks later.
We have now been together for 17.5 years, and neither of us have ever been unfaithful, and we both know that if we did, it would be the end.
ExH, on the other hand, has cheated on every other woman he has dated since me.
So personally for me, I'd be off.
That said, one of my close friends caught her DH full on cheating in 2000. He was having daily sex with a colleague - they went to her house every lunch time. This went on for 6 months, and it only came to light because the OW sent my friend all the e-mails between them. She forgave him, and they are still together to this day. So, things can be salvaged, if that's what you want.
Would I be happy with that? No.
I think that with time, you'll know what to do, even if that's a few years down the line.