One of the first things you try to figure out when you find that your man has been cheating on you is whether you should stay with him or not. I’m not a therapist, but even a therapist won’t come out and tell you what you should do. What they (and I) try to do is to get you to look at the facts and the issues and come to your own conclusions.

However, sometimes, especially when you’re in the midst of a crisis, it’s hard to see those facts and issues. Your emotions are through the roof, and you can’t face the facts, not to mention deal with the issues.
So the first thing you should do is try to stop the carnage. Step out of panic mode and tone it down a few notches. Give yourself some time to calm down and think. That’s not easy, because you want to do something to make yourself feel better, or make him feel worse, but that’s not in your best interest.
The next thing you should do is consider your own feelings. What exactly is it that you’re feeling? Obviously, you feel betrayed. You’re hurt, angry, and embarrassed, just to name a few of the myriad emotions. But why do you feel that way? Do you really love him, or are you just afraid to be alone? Is it that ‘I don’t want him, but I don’t want you to have him, either’ thing? Or are you just angry because you can’t believe he would have the nerve to be with another woman?
Sometimes it’s hard to figure out whether you love someone or if you’re  co-dependent. The lines get blurry. For that reason, I recommend that you read Women Who Love Too Much by Robin Norwood. It’s an excellent book that can help you figure out what you’re doing and why you’re doing it.
If you think you love him, the next thing to figure out is whether or not he loves you. That’s a tough one. He might say he does one day and say he doesn’t the next. In that case, I’d say the writing is on the wall. In other words, if he doesn’t know from one day to the next whether he loves you or not, he probably doesn’t, and just doesn’t want to tell you. It’s difficult to tell someone you don’t love him or her. If he says he loves you, but he doesn’t act like he does, he probably doesn’t. And if he doesn’t, I’d say you’re most likely better off without him. I mean, you don’t really want to be with a man who doesn’t love you. Do you? I know I don’t.
Let’s say that you do love him and he is convincing you that he also loves you. He says he’s willing to put the other woman out of his life, having no more contact with her at all. Can you trust him? Should you trust him? If he gets annoyed when you ask where he’s been, or if he has a problem giving you his email and social media passwords, then you probably shouldn’t trust him. If he hides his phone from you, or if he leaves the room to take calls, you definitely shouldn’t trust him. And if you can’t trust him, do you want to be with him? I wouldn’t, but that’s a decision you have to make.  (See 16 Signs That He Is Cheating.)
What if you love him, you believe he loves you, and you think you can trust him (or at least, you’re willing to give it a try)? Consider the kind of person he is. Is this just another piece of your heart that he’s torn out by cheating again? Is he an addict/alcoholic? Is he immature, meaning, does he still have to go out at night “with the guys,” which usually means hooking up with girls? And most importantly, is he abusive in any way? If you answered yes to any of the above, stop! Immaturity is the only one of those things that might get better as he gets older, unless he gets professional help. In the mean time, do you want to deal with those things? I hope not! None of them should be tolerated!
What if he wants out? If he wants a divorce or a break-up, give it to him! Nothing good can ever come from holding onto a man who wants to get away from you! Trying to hold on to him will only make him angry and resentful, and that won’t help anyone. Let him go, even if you think it will kill you. It might feel like it’ll kill you, but it won’t. 
What if he wants to make it work? Was it just a one-time thing? Is this the first time he’s cheated in a long relationship where he has otherwise treated you with love and respect? Is he normally an honest person? Does he take care of you and your children? Is he a good father? Does he feel remorseful? Is he willing to do whatever it takes to make your relationship work? If you answered yes to these questions (or most of them), maybe you should give the man another chance. Especially, if he treats you with love and respect, he might be worth holding onto. I’m not saying you should trust him after the infidelity. Trust is something he should be willing to work to build again. But maybe you should consider giving it another try… taking baby steps.
Can you forgive him? This one is really important. And it’s more important for you than it is for him. Regardless of whatever happens between you and him, forgiving him sets your heart free. It allows you to let go of the pain and go on with your life, whether it’s with him or without him. But if you choose to stay with him, and you’re not able to forgive him, it won’t ever work. Forgiveness is essential. (See Queen of Unforgiveness.)
How would staying with him affect your self-esteem? Could you respect yourself if you stay with him? Sometimes it’s hard to know at first. This one might take a while to realize. Don’t confuse pride and ego with self-respect. Pride is not good, but self-respect is necessary. If you feel ashamed, or that you’re stupid, or crazy for being with him, maybe you should pay attention to those feelings. That’s not to say that you are stupid or crazy, but those feelings could be telling you something. Maybe your heart is tired of being his punching bag.
I suggest that anyone faced with this decision get some counseling. It’s a huge decision, and it can have life-altering effects. Making that decision while your heart is shattered into a million pieces is not advised. Talking with a therapist can help you to sort through the issues, try to put the pieces back together, and figure out what’s best for you.
If you’re married, consulting with an attorney is crucial. If you’re thinking that you do want to end your marriage, do NOT do anything until you speak with an attorney. Making moves prematurely can be costly, so don’t make that mistake.
Deciding what to do when you find that your man has cheated is an extremely difficult thing to do. There’s no way to know for sure what another person is feeling or thinking, or what they’re going to do. That’s why you have to focus on what’s best for you. YOU CANNOT MAKE THIS DECISION BASED UPON WHAT HE WANTS OR WHAT YOU THINK IS BEST FOR HIM. HE obviously wants his cake and to eat it, too. You can’t allow him to have that. Love yourself enough to make the choice that is good for you. It’s going to hurt like crazy if you decide to let him go, but in most cases, it won’t hurt nearly as much as staying with him.
And if you’re the other woman, you should never stay with the cheater. Remember, he’s cheating on you, too!

Get some counseling and figure out your next move. Don’t just ‘let sleeping dogs lie.’ In my opinion, they’re lying, whether they’re sleeping or not! ; )