I've had a similar situation, and as someone that is quite a few more years on down the line from you, I can tell you that you never get completely over it.
I sometimes think it would have been easier to have left, and if it was my daughter I was speaking to I would advise leaving now as the chances are that it won't turn out well.
We're still together (happily) and he is a better person BUT I will never trust him or anyone 100% as that innocence has gone now. I've often thought that I could trust him completely with my life but not my heart. That's why people that cheat piss me off so much, there are so many repercussions that they never think or care about.
All in all, I'm glad I didn't leave, we now have a happy family with 3 lovely kids and he would do anything for us.
So I deal with it and when it rears its ugly head, which it does occasionally, then I wallow for a while and try to move on, until the next time. It's my cross to bear I suppose as I made the choice to stay.
And by the way, even though it sounds bleak when laid out like that, I now go for months without thinking about it, so it's not as if I'm sitting here sad about it every day.