Ok, you need to relax and be cool, what can you do that can help you achieve this? Remember, you spend every weekend with this guy (I think?!), think of it that way.
It is fine to prepare for the worst but not to expect it; you have read what Michelle says about the self-fulfilling prophecy? If ever you needed to act as if the time is now
From what I have read about other DBers that have gone for counselling with their h's it is your chance to show that you can listen to him. DBust to the max i.e. don't defend yourself, this may be a chance for you to get some information.
I wouldn't look at this as the 'be all and end all' or the end, it is part of the process, whatever that process is.
I understand your stress and nerves though. However what is your plan for the meeting, how are you to going to act?
What you said to me about my h... My DB coach said that the general rule with WAS is that women build up a huge case against their h and when they leave they are angry and have made up their mind. With WAH's they often leave on a whim and do their thinking afterwards which is often why they are so quiet, they just can't give answers.
I understand why my h left, he had just gone through a life changing illness very young and I don't think he has processed it all yet, plus that summer I was acting like a bit of an idiot. I have since stopped and I actually really like that he doesn't know why he left because I have managed, through consistent DBing to break down the perceptions of me that he left with. Sorry, I am an eternal optimist!!
My DB coach said a major characteristic of WAH's is their guilt and feeling like the bad person. That is often why they can't talk about personal stuff because of their guilt and shame. It is quite a huge hurdle to get over, just something to bear in mind during your counselling.
Your husband cheating was not your fault. I think with my h, he may not have been having a PA but I strongly suspect an EA. She was around when I left, I know that much!
I accept 50% of the things that were failing in our marriage but I hold him 100% responsible for leaving and for his subsequent actions. I have forgiven him though, I can't seem to help it.