Sorry to see you here, Magellan, but welcome. 
I was in a similar situation over a year ago, 19 years married, 3 kids, busy lives etc. Sex was never an issue, but connecting emotionally was always an issue. So she dropped a bomb that she had been having an affair with a woman from the gym (who is married to a man). It was emotional, but that is FAR worse than physical, because it requires you to wake up daily and CHOSE to continue cheating and not tell your partner. I actually got over that part, but when I realized she had been lying about still connecting with the woman, my eyes were opened.....she could and had lied about so much. All the red flags were there the entire time, but I ignored them.
All that said, I eventually found her online profile. It did not state "looking for women, or bi, it stated looking for men". So while she goes everywhere with her girlfriend (who looks like a man), it appears she searches online for men. My conclusion is that she did not want any of the responsibility of breaking up the family/marriage, so she is saying she is gay. Is she? Probably not. Maybe bi-curious? End of the day, it does not matter to me. All that matters is the person that was closest to me could lie to my face daily and do it extremely well. Do I think she has been lying the whole time? Probably...doesnt matter. 
If you go back to August 8th 2022 and read my first post, it was like yours. "My marriage is amazing, solid, wonderful kids, etc". I am not saying yours is not, but making time for yourself and allowing you to see the past without interference can be a mind blowing experience. You might just find this has been a toxic relatonship for you the entire time. 

All of my health issues disappeared, no more xanax, etc within weeks of going LOW contact with her. She is now trying to get us talking again, I will not. She is a broken person and she showed me who she really was and I wont go back.
I hope you find the answers you seek and find a path that suits you. Keep your kids top of mind, you have to be healthy and strong for them. Stay the course, its hurts but on the other side is fulfillment and happiness!

Be well

Thank you all for your feedback!  truly encouraging and life saving really.  My why in life is now gone.  I am here because of my two young kids and that is what i will focus on, aside from my own self development and healing.  

I pray for all of us who has been caught up in this.  Chin up, one day at a time, small improvements, stay consistent and find support.  They are out there, you just need to reach out.  I love you all, my brothers and sisters in heartaches.

My Future Ex-husband (legally separated) says he's bisexual. He spends ALL of his free time at a gay couple's home. He takes trips with all gay men. They are always getting together to celebrate holidays and birthdays. He has a deeper connection with one of the men (Bill). My GID Ex  'says' it's not physical with Bill but it's more of an emotional connection which I don't believe is true. At this point, it doesn't matter!  It's all unacceptable IF you are married and took vows to love and cherish your spouse! 

Magellan: I think it depends on the person.  When I confronted my husband, I was expecting him to come up with a story about not realizing he was gay until after we were married.  It's not that I would have believed him, but I figured he was just in denial.  Instead, it was even worse, he said to me "I have always known that I was bisexual."  I mean, the man had NO attraction to women.  I went for over two decades without sex from him, the issue was NOT bisexuality.  I can only guess that at some point he convinced himself that as long as he was capable of occasionally gritting his teeth and fucking a woman, that was good enough to call himself bi.  

It's not just that he lied to me -- really he lied to himself and then told the same lies to me.