I'm just going to copy and paste here. Take what you need or what applies to you or can help you.
First off, know that the affair is not your fault. Have you been the perfect husband? Of course not, no one is. She had other options besides cheating, such as communicating with you on working out the marital problems, going to Marriage Counseling (MC), etc. Yet she chose the easy option: cheating. Most likely because the Other Man (OM) stroked her ego and provided the shoulder to cry on. Your wife is now a Wayward Wife (WW), so consider as such. She will give the common excuses: You weren’t there for her, OM provided for her needs because you couldn’t, etc.
The last thing you should do is to cry, beg, and/or plead with her. This not only makes you unattractive, it drives her away. Trying your best to be the best husband doesn’t work either, because you cannot compete with the fantasy she has built up with the OM.
Now you have to play detective in order to save your marriage, or to get the proof you need to end it. If you can afford it, hire a PI. If not, you will have to do this on your own. What you need to find out is if this is an Emotional Affair (EA) only, or if this has progressed to a Physical Affair (PA). What you also need to find out is who exactly the OM is, his identity, if he’s married, and if he’s married, his Betrayed Wife’s (BW) contact information. You will need this info later on.
What you should not do is confront her too early about the Affair (A). You are going to need to gather all the information that you possibly can before confrontation. We Betrayed Spouses (BS) call this investigating. Others call it snooping. The cardinal rule about investigating is NEVER REVEAL YOUR SOURCES!!! This will prevent her from denying the A, which they almost always do at first until presented with proof of the A. This will also prevent her from gas lighting you. Gas lighting is a term used when the WW, when confronted, will say that you are just jealous, imagining things, and that you are just crazy. Gathering enough proof of the A, also prevents the Wayward Spouse (WS) her, from giving you the Trickle Truth (TT). TT is when the WS minimizes what they have done in the A, and will only admit to what they think you know. For example: Most will say they only kissed their Affair Partner (AP) once, when in fact they went much farther than that. If the A has gone to a PA, they usually only admit to doing it once & with a condom!
If the WS is using a computer as part of the tools of the A, then you will need to install computer monitoring software, the basic ones are keyloggers. There are free ones, which basically only record keystrokes, to the more expensive ones that record keystrokes, capture screenshots of the computer, email you the results, etc. There are good ones like Spector Pro, Web Watcher, Spy Agent, etc. There are also free ones, but you get what you pay for. Why do you need a keylogger? So you can be aware of their communications, such as how long this has been going on, what they have done, and what they are planning to do. Another key tool cheaters use is the secret email account. A keylogger will capture their usernames and passwords.
Now you might feel guilty about investigating/verifying. Sorry, but their privacy went out the window the second they endangered the marriage by having an A. It is your right to investigate now, so don’t lose any sleep or feel guilty about it. If they try to turn it around on you (blame shift), tell them it’s your right because they are having an A.
Another tool that cheaters use is the cell phone of course. Some carriers allow you to check online who the other person is calling and/or texting. If you don’t have access to this information, then use the keylogger to obtain it. If your WS has a smart phone, you may be able to install phone monitoring software such as Mobile Spy or Mobistealth. This will allow you to see their text messages. The more expensive versions of Mobile Spy and Mobistealth even allow you to listen in on their conversations in near real time, and use the GPS to track their location. If your WS suspects that you are on to them, they may purchase a secret cell phone. A clue that your WS has a secret cell phone is if they suddenly leave their regular cell phone lying about when before they were guarding it at all times. This brings me to the Voice Activated Recorder (VAR).
A VAR can be purchased very cheap, usually around $40 or more, at either Walmart, Best Buy, or your local electronics store. A VAR can be very useful at determining if your WS has a secret cell phone. Also, a strategically placed VAR can be very useful if you are unable to install phone monitoring software on their cell phone. A good place to hide a VAR is in the WS vehicle. If there is one place they feel secure in talking with their AP, it’s in their vehicle. Some place it under the drivers seat with industrial strength Velcro. It’s up to you where you can place your VAR. You may want to hide one in your bedroom or the bathroom in order to record their conversations.
Once you have gathered your proof, it is time to confront your WW. This is called the Day of Discovery (DDay). This may well be the most traumatic day of your life. If you have gathered enough proof, your WW will not be able to deny, gas light, or TT you. Your WW will either go into crying fits, be angry, or both. She will try to blame you for the A, tell you she has been unhappy for months or years. Re-Writing the history of the marriage is a common tactic, they use it to justify the A to themselves. Stay strong and know this is not your fault! This is hers!
She will say that she does not know what she wants. This is called fence sitting. She wants the security of marriage, but wants to play around with her OM. Do not stand for this. It is either you or him. There is no room in a marriage for 3 partners.
Another common occurrence is that the WS will leave the house when confronted on DDay. This is usually only for a few days or weeks. The WW will usually contact the OM about what happened. The WW usually comes home after a few days, but sometimes they don’t. DO NOT beg her to come home. Like I said earlier, this makes you look weak.
Another common tactic that the WS does is to cry and plead that they want to fix the marriage after they have been caught, but then they take the A “underground”. This is when the WS has talked to the AP about ways to continue the A without your knowledge. This is usually when they resort to using a secret email account and a secret cell phone. If you have not revealed your sources, then you can usually find out if they have taken the A underground.
If they wish to stay in the marriage, then you have to remain firm and demand No Contact (NC). They must end the affair and go NC. That is the ONLY way to save your marriage, by killing the affair. An A is exactly like a drug, because the WS receives a “high” from the affair. Feel good chemicals like dopamine and others, are excreted in the brain during the A. Giving them a high feeling, the feeling of being in love, etc.
If your WS is very deep in the fog of the A, and refuses to go NC, or the OM/OW refuses to go NC, then the next step is exposing the A. This means contacting the other BS. This serves two purposes. This helps kill the affair by bringing it into the light of day, and you have another set of eyes watching the other side of the affair. You might even be able to compare notes with the BS and find out more information, or they may have information about the A that you didn’t know about. The other reason is because it’s the right thing to do. Wouldn’t you want someone to have told you what was going on?
Remember the monitoring I was telling you about? Monitoring the WW will allow you to know if she has broken NC. If the OM contacts her and she doesn’t tell you about it, that is also breaking NC. And if you ultimately decide to Reconcile (R), then monitoring will help rebuild trust. After you keep finding nothing, and she is doing her part in R, then you will find yourself monitoring less and less. Eventually you may be able to wean yourself off from monitoring her since she has rebuilt some trust.
Try reading these too:
The Betrayed Spouse Script Bill Of Rights - For The Betrayed 
EA or im just Crazy 
