I'm sorry this happened to you, but I'm glad you found this place. There is a giant amount of crowdsourced wisdom in terms of dealing with infidelity on this site. All of the posters here have been victims of infidelity in various ways, and we all post here voluntarily, and anonymously, because we want to help our fellow victims.
First step for you is to start browsing The Healing Library (yellow box, top left of this page). There is a ton of helpful stuff there.
I would suggest you read other threads on here. There is a long thread by a poster named "Walloped". If you can find that, read it.
Your approach so far has been diametrically the wrong thing to do. I say that gently, but bluntly, because what I want for you is to heal. MC (marital counseling) immediately in the wake of infidelity is almost always totally unhelpful, at best, and usually it is harmful.
Also, not talking about it is the worst thing you as a couple can possibly do. We call that "rug-sweeping". It is a guarantee that this will fester and rot in your heart and it will become worse, not better.
As a BH (Betrayed Husband), your WW (Wayward Wife) has inflicted a trauma to you. If your marriage is to become a healthy one, you need to heal from that trauma, and she needs to acknowledge her role in causing it. Think of this as if she had snuck out of bed one night as you lay sleeping and smashed your femur with a sledge hammer. First and foremost, healing works best if the two of you discuss the affair often, openly, and with blunt honesty. This includes you venting your rage. Yes, rage is normal and even healthy for a BH. Keep in mind that millions of women are married to men who work hard, and remain married without fucking other men (never mind students in the school where they work). In fact, for most women, having a husband who works hard is a desiderata, even a wet dream.
Two good books to read (both you and your WW):
"Not Just Friends"
"How to Help Your Spouse Heal from Your Affair" by Linda MacDonald.
I can tell you that a WW cheating after feeling neglected by a BH who works a lot is one of the most common themes here on SI. The first thing you should allow yourself to acknowledge is that this is totally fucked up bullshit logic on her part. You had NO ROLE WHATSOEVER in her decision to fuck another man. If she felt like she wanted more attention from you, it was incumbent on her to communicate that and take steps to make the marriage more affectionate. NO MATTER WHAT YOU DID, no matter how many hours you worked, her decision to fuck another man was a completely broken, horrible, and stupid decision by her.
Your marriage can only heal if she acknowledges this, takes ownership of it, and seeks IC (Individual Counseling) to figure out what is broken in her moral compass that would lead her to make such a wicked choice. Keep in mind this was her choice. Do NOT let her get away with calling it a "mistake". A "mistake" is putting 1 tablespoon of baking soda in cookies, instead of baking powder. Or locking your keys in your car. A woman does not find another man's dick inside her vagina by mistake. She must make dozens, perhaps hundreds of decisions and choices to sneak around, lie, gaslight, and deceive, never mind betray her marital vows, before she takes off her panties and chooses to let another man inside of her.
I say it that way because the strongest urge of a newly minted BH is to go back to the "before time", to the marriage you thought you had with the woman you thought you loved. Your first task is to face the grim reality that you can never go back there.
In fact, the woman you thought you loved never existed. The real life flesh and blood woman next to you, your wife, is the kind of woman who will decide to fuck another man if she feels she isn't getting enough attention from you. We know she is that type of woman because that is in fact what she did, and I don't reckon she has sought counseling to fix what is fucked up inside of her.
She is not a safe spouse until she does that.
Big picture. You were married for barely three years, with no kids, and your wife decided to fuck another man. Now that you have a son, the stress and burden of family life will be 10 times what it was in the first 3 years of your marriage. If your wife cannot keep her panties on merely because you work a lot (and presumably she enjoys the material benefits of your earnings), how many other men will she fuck when you add the stress and strain of raising a son?
Yes, her A (Affair) was a symptom of a "bigger problem", but not the "problem" she is trying to blame -- you working. The "bigger problem" is a WW with poor coping skills and loose morals who would rather lie to you and cheat on you than work with you to try to make the marriage better.
I would strongly suggest that, in the Healing Library, you read about and implement The 180, and also that you read and print "Joseph's Letter" and give it to her to read.
Good luck.
By the way, "sex three times in the back of a car", that is almost certainly complete bullshit. Almost every WW who has ever been caught in an affair has said "we only had sex three times". It's utterly cliche, and almost always a lie.
You should start considering what you need to heal. For most BH's, this includes:
A complete written timeline from her about the A, including all of the "nitty gritty dirty details" of her sex. Since it occurred within the past 20 or so months, she should be able to corroborate most of it with her texts/messages/emails to the POS she was fucking.
Complete device/account transparency, with your unfettered ability to read, copy, and review anything and everything she sends to or receives from anybody.
Complete ownership by her of her fucked up choices and a sincere effort to figure out why her moral code is so broken, and to fix it.
Finally, and most importantly, true remorse, which is built on empathy -- a sincere effort to understand your pain and trauma and to help you heal from it. This starts with patiently and completely answering all of your questions about the A, over and over and over, as many times as you want to ask them.
[This message edited by Butforthegrace at 12:17 PM, December 30th (Monday)]