Hi sidechannel. Sorry you find yourself in need of a site like this, but you've come to a good place. A lot of very experienced caring people are members here.
Now, your wife is still having an online relationship? That's a complete dealbreaker. Don't accept this, not for one more second. She doesn't get to keep her boyfriend while you sit on the sidelines and 'support' her because she's going off the deep end. It does sound like something has snapped, but that doesn't mean you are required, or even expected, to stand by while she cheats. No one is expected to support that.
The days where you are wondering why you can't keep things in perspective? That's your brain bargaining - you want things the way they were, and if only you could get over this, they could be, right? WRONG. Your wife is cheating. She may not be physically cheating, but she is most definitely in at least one emotional affair. That is not the path to a happy marriage.
She doesn't want to leave, and she doesn't want you to. Well, she can have that (you both still at home) or she can have her online life.
First I'd recommend some software that will let you see where she goes online and what she writes, and what is written to her. There are many out there, and there are programs for the phone as well. This way you will know what she's doing, and what you're up against.
Second, the EA stops, NOW. Either that, or you are separated. This isn't negotiable. If you are to work on your M, then your wife cannot be in another relationship. I suggest you see if she will read a few books on the subject, or some of the articles in the healing library here. There is a great 'faqs' section for WSs (wayward spouses) that will help her see what is wrong with her behavior.
Third, see an attorney. Consultations are often free, and you need to know what your rights are, and what you should legally do to protect yourself. You may think "but I don't want a divorce". No one said to get divorced. Just talk to an attorney to see what is available, nothing more right now.
Fourth, start the 180. It's in the healing library, Faqs for the BS (betrayed spouse), question #11. It' for you, it helps you regain your strength and sanity when the affairs are stripping both away. It will help you clear your head and gain perspective. Meanwhile, it will show your wife that you are not kidding about your needs and boundaries, and that either both of you are in this marriage, or neither of you are. Right now, she has one foot in and one foot out, and you're hoping that she pulls the other one in.
Cheaters are very selfish people, at least while cheating. They will justify cheating as their right to be happy. They will blame the BS for anything possible. They will claim it 'just happened'. Nope, they are selfish, plain and simple. They cheat because something in them is broken and they have very poor coping skills, so they take the easy, cheap way to feeling better - external validation. That's what an affair partner is - external validation. This is NOT your fault, in any way. If she was unhappy, she had so many other means to deal with it. She chose full on destruction. Not good.
Your priority now is you. Take care of you. Sleep, eat (or drink some Boost or other nutrition drink), try to go for walks. Remember, none of this is your fault.
And please, you cannot 'nice' your wife back. She is lashing out, and she is enjoying the external validation. She is so selfish that your pain is irrelevant to her. She will care when looking at you, but not enough to stop the behavior - it feels too good. If there are no consequences, not real negative effect, then why on earth would she stop? Because she suddenly realizes it's wrong? Because you are so nice and understanding? No, no way. You have to have boundaries, and she needs to understand that you will not accept more than 2 people in your marriage. She is using the computer to turn your marriage into a group effort. That is not what you signed up for and it's not what you want. If she feels no loss, she won't stop. She's known it's wrong since day 1. That doesn't matter. SHE is what matters to her right not. She needs to see that she won't have her happy home life and her internet sexual escapades.
Good luck, and keep posting - vents, questions, etc. This site really is filled with caring, knowledgable people that have been where you are and can help guide you through the hell-maze of infidelity.