Welcome to SI, glad to meet you, sorry that you had to find us.
Head up to the yellow box, upper left, and check out The Healing Library. In it are links to Abbreviations, the BS FAQ (item #11 of which, The 180, is often recommended here), the WS FAQ, online Articles and (mostly) print Books.
There's a true observation on the site, "you have to be willing to leave the marriage in order to save it." This is a true saying. As long as you are not prepared to completely walk away then you're giving control over outcomes over to your WW (Wayward Wife). If the ultimate loss if the marriage is not on the table then what reason could she possibly have to stop what she's doing? Because she's nice? Based upon evidence, she isn't nice right now and she's got no reason to go back to it.
If you haven't already, you're going to start riding The Emotional Rollercoaster. Your emotions will swing wildly from rage to hate to anger to love to (maybe) crying sadness and horrible loss. This is natural. I repeat myself, this is _natural_. Don't be ashamed. Do keep your hands and feet and head inside the car at all times. Enjoy the ride, it'll be brutal at first and then calm down for a bit. Then it'll get brutal again, but for not as long.
If you want to react appropriately you have to analyze the real situation here. She has feelings for another man. This has impacted her feelings for you. You are in love with her, but she likely isn't in love with you right now. She might still love you, "like a brother." This is what leads to the famous line, "I love you but I'm not in love with you" (ILYBINILWY). Brutal to hear.
She's been detaching for a while. Right now _you_ and her family are _not_ her primary concern. You've become, to her, just like every other man on the planet. She just doesn't really care. You, however, have one disadvantage here - You're "in the way" of her being with (in her mind) the man that she is having feelings for. Since you're a barrier she will, naturally and hurtfully, resent you. Her respect for you will drop and you begging and rushing around trying to save things will make you appear weak in her eyes and she'll resent you even more.
Crazy? Yes. natural flow of events in this situation, Yes again.
We have a fair amount of Christians on this site whose WS (Wandering Spouse) was involved with either a Church leader or another parishioner. You have uncovered the feelings, but you haven't uncovered the whole truth. By the way, take pictures on your phone of her notebook and then email those pictures to some email that she does not have access to. She's likely to go a bit ballistic when you reveal what you know and try to erase all of the evidence and convince you that you're crazy/it wasn't that bad/whatever. That is known as "gaslighting", from the play, "Gaslight".
She might also promise to never do this again and just let it go, known as "rugsweeping." Things swept under the rug grow and fester in the dark and come out years later all sharp teeth and big fangs and cruel claws. Don't rugsweep.
Frankly, my best advice to you would be to go over to the Pastor's house, with proof, and sit Pastor and his wife down and show your evidence and tell your story. This gets at least Pastor's wife on alert that another woman wants her man. Pastor should, again frankly, recuse himself from counseling on this since he'll be appearing to your wife as some sort of Knight In Shining Armor, trying valiantly to save a marriage that she no longer wants.
Go read The 180 (item 11 in the BS FAQ in The Healing Library). It is for _you_ to detach a bit so that you can more accurately assess and deal with the situation.
Good luck. On this site (( )) are hugs and I do the fist bump }{. Have a fist bump }{