Sorry my friend.  

Now you know what the future holds and you can begin moving forward with clarity and cause. 

I know how painful this is, but you will be ok and your kids will be ok.  You've got this!

My advice:
1.) If you are having trouble sleeping, eating, anxiety attacks, etc... go visit your Dr. first. 
2.)  Lawyer - most offer a free or very low cost initial consultation.  Go see a few of them.  Write down a bunch of question in advance and learn as much as you can.  Then when you are ready to pull the trigger you will have a favorite already selected. 

Bank - Most judges will frown on you making any big changes to your banking setup just before filing... BUT if you think your wife will steal or mis-use your joint funds, then you could protect those funds.  Just don't try to "hide" them, so to speak. 
Marital counseling doesn't seem to be an option at this point (from what I read).  At least not in the direction of saving the marriage.  However, going to counseling could be helpful because it's a third party referee to help you get through some really hard communication.  You may not be able to fix the marriage, but if you can get through some hard conversations now it might make things go smoother in the future. 

I have a different take than Phoenix on the bank account.  Daryl may be right, in that your wife may have spent some time last week figuring out what of the marital assets she's entitled to.  If she did consult a lawyer, or more than one, those lawyers will not be able to work with you (it's called "conflict of interest," and whoever you call for a consultation will have to check to make sure s/he hasn't already met with your wife.  If you live in a fault state, whether your wife has acted and is involved with another woman may work to your advantage in negotiating a settlement and custody, especially if she doesn't want her sexuality made public.  If you live in a "no fault" state, then it's 50/50, assets and debts.
  Contrary to Phoenix, I'd like to suggest that you consider opening the bank account.  You can check with a lawyer on this next bit, but I think you would not run afoul of a judge if you transfer half (or even all) of your savings into that account--BUT don't touch it.  Just park it there.  This may be a necessary self protective strategy if you fear your wife may feel "entitled" to help herself to your joint money.  
  And like Daryl says, don't feel guilty.  You are not breaking up the marriage.  She did, by changing the terms of it.  You don't enter into marriage expecting to divorce, but sometimes circumstances make it necessary.  

Thank you all.  I have to be very careful in what I can do which finances and any benefits my wife receives regardless of her actions. 

I am active duty Military and she can go to my chain of command if I remove her acess to funds as well as spin whatever narrative she likes.  I have been upfront with my command team about everything from the start.  They are supportive. 

I flew in yesterday and my wife had said I could find my own ride home from the airport but I thought I would see or hear from her later.  She never came home yesterday and never called or messaged once.   How do you go through such a change?  She in July was still referring to me her as husband and Best Friend. 

This Thursday marks our 15 year anniversary, I submitted my leave and took this week off originally so we could do a trip together just the two of us. Now I’m spending in to go open single back accounts and hire a lawyer.  It’s all so surreal.