I don't have a lot to add to what has already been said, I would emphasize the comments that BreakingBad made, forgiveness does not mean you stay together.
Forgiveness also does not mean that you forget and everybody acts like it never happened.
Unfortunately, some people expect that once you have forgiven them that you will act like nothing has happened in the past, and they fall back into their old behaviors, noncommunication, etc., and the relationship goes back to those "dark times".
My wife worked really hard in counseling, for years, but she still tends to lapse back into not communicating, not talking, and some old behaviors resurface. Those behaviors are really hardwired in, and you have to think very carefully about your behavior and actively work to behave differently.
I realize I'm not saying this very well, but it's just extraordinarily difficult to communicate the amount of change that someone has to make in order to become a trustworthy partner after they have betrayed someone in this manner. As many others have said, it's not the sex, it's the lies, the deception, the gaslighting. My wife's lying went far beyond her affair.
Take this one day at a time, make no commitments that you are not absolutely certain you want to keep, and don't decide to have children just now as a dysfunctional response to all of this. Having children does not make dealing with the infidelity easier. It does make everything harder to deal with, and the consequences much worse and far ranging.
Yes, I would also emphasize that you almost never get the real truth at first, for even if you get the truth, you there are a lot of things that are not disclosed. My wife insisted that this guy was "just friends", insisted she was not cheating on me, screamed at me over it, I mean, really, how could I be suspicious of her the mother of our four children. Even after she confessed to having sex with him, she made up an entire false history of their sexual behavior and encounters. Told the story to her counselor, told it to our marital counselor, and of course told it to me, even though it didn't make sense to me and didn't fit, the circumstances at the time. When she finally confessed completely, the story was extraordinarily different.
Yet the same person sat in a marital counselor's office, for months, week after week, and accused me of not believing her, of not being able to handle the truth. All while insisting that she had told us everything.
[This message edited by standinghere at 7:09 PM, Thursday, July 4th]