First, I'm very sorry for the pain you're in. Infidelity is special kind of shock and trauma and you need individual counseling for yourself to deal with it appropriately.
So her child is not yours. Not knowing the laws in your state, I cannot say for sure, and you'd need to check with an attorney -- but it's likely unless you legally adopted your child you may not be on the hook for child support if you divorce her.
Your best bet is going to see a family law attorney to see what your options are. Having lost 80 pounds and a now trimmer you with trade school behind you and solid employment, you probably have a lot more options among women than you think you do. And many of them are fine, quality women who would never do something like this to you.
So I second, third and quadruple what others have asked, which is what do you want? Is she truly worth your time any more? If you try to "reconcile" you're signing up for years of eating the shit sandwich. Having done this myself, I can tell you it's a very grueling experience. On the other hand, divorce has its own special challenges and pain. However, it does seem that on balance, most people who divorce earlier move on and heal more quickly.
Marital counseling is a completely useless exercise in these situations, and your MC doesn't have a clue about whether your wife is remorseful or not. Your MC sees it as his/her job to "patch up" the marriage. Well, your wife killed the marriage. She plugged two rounds in the head and buried it in a shallow grave. An MC will push for rugsweeping and will even enable blameshifting on to you. I speak from personal experience.
Your WW is also exhibiting some stereotypical patterns. Most of us can spot minimization a mile away. When a WW or WH says "only kissed" or "sex only one time" or "just oral" they are often minimizing. Not all the time, mind you, but most of the time. It is likely your WW is selling you a narrative that is inaccurate. The fact that she is already claiming only months out that she doesn't remember or know dates etc is a very bad sign. It's a huge red flag.
Also, I hate saying this, but it sounds like your WW simply was in lust for Mr. Bodybuilder. Don't over complicate this. The reasons for infidelity aren't all that difficult to suss out. It's an old sin that has been with humankind since the beginning. They understood it 5,000 years ago very well. They understood all about the lies, minimization, blameshifting, trickling out the truth, how a guilty party would try to flip the script and DARVO you (look it up). It's all ancient, primeval behavior. There's nothing new under the sun.
The fact is your WW saw an opportunity, she was attracted to him, she actively took steps to make it happen, and she thought you'd never find out. She gave herself to this man willingly. She took countless steps to betray you. She made the decision to lie to you countless times. She lied directly to your face countless times. She threatened your very physical health.
Now, as others have said, the good sign is she confessed to you before you found out. But that may have been because something was going to come out, or she was worried about something being revealed, so she too preemptive action to control the situation.
But there's no doubt that she locked you down as a provisioner for her as a single mom -- and once that was achieved, she looked around and found a hot side piece. This is no different from a man doing the same thing and taking his stable, loyal wife for granted while he lines up a 20/30something woman as his mistress. One has to ask whether this was the first time, or certainly whether it will be the last.
I don't say this to hurt you or cause you additional pain, but just to get you think about this all from an outside perspective. What would you tell a friend of yours who found himself in a similar situation?
Since you are probably not getting the full picture, it's very difficult to reconcile in the face of that. Trust has been shattered. To restore it, both full transparency and some kind of recompense in some form are required. Without transparency, no trust. Without trust, no reconciliation. And then you're just limping along in limbo. You already know what a version of limbo feels like 5 months out. Imagine another three years of this.
You can save yourself some time by probably just filing for divorce. But if you want to keep going with this, she will need to at the very least:
1. Submit to a full STD panel
2. Write out a detailed narrative timeline for you with names, dates and details.
3. Submit to a polygraph to verify the truth of the timeline.
Then and only then will you really have a better idea of what you're dealing with here and whether it's worth your time.
Is it worth your time? She is already heading for the hills and practicing avoidance, another bad sign. She's losing patience with you. She's blameshifting. Yet your MC wants you think she's remorseful. Really?
I do recommend what DicttumVeritas has said - visualize yourself without her, divorced from her. Take it even further and visualize yourself living in a dumpy apartment, driving a rust bucket car. Not that that will happen, but just visualize it. I did this, and felt tremendous relief. I wasn't overjoyed with this mental picture, but it gave me a sense of freedom and buoyancy. It wasn't because I don't love my wife or even find her companionship enjoyable. I do, even after everything. It's because she wasn't willing to go all the way with me and provide me with the full truth. And because she herself is a constant physical reminder.
When you think that through you might decide being without her is the better of two options.
[This message edited by Thumos at 12:53 PM, August 17th (Monday)]