I hate to read this, and as many have said, Prince, this is totally familiar to many of us.
In my case I caught on early, we had the chat, we had the promises, we had the failure to stick to the promise, we had the confrontations, and we had the divorce.
What you feel and what you want are all totally
valid.
The problem is that none of what you feel and want is
relevant.
She wants to be chased. And she's prepared to put her relationship on the line to be chased. That to me makes it sound like no matter how much she protests, she hopes to be caught.
The only way I'd say she doesn't hope to be caught is if she knows she's already been caught.
Can I ask - has she become more sexually active with you? More extreme? Done "the thing" you always hoped for but she always refused (with my ex it was a sudden conversion to her wearing lingerie when I got home from work, and actually WANTING to have my cock in her mouth after 17 years of thinking it degrading and wrong)? If these things are true, then she's already fucked him, and is probably doing it every time she claims to be out with workmates.
If you are determined to check - I suspect that there will gaps in her phone calls to him on the nights she claimed she was out with the girls, but long calls on nights she went out with you, but visited the loo mid-evening.
Unless she is first willing to end the destructive behaviour, second willing to fix the issues with you, and third willing to put herself beyond harms way, then it's over.
Your marriage is dead, my friend, it just twitches for a while. And that's the saddest thing I've said to anyone on this board.
You are doing the right thing in getting psych help though, you seem to be going through
the five stages of grief, and maybe you're at "Bargaining".
I wish you well. Be strong and it'll be OK.