Hi L.,
Marriage counseling, or any other counseling can only be as successful as you make it to be. It sounds like you and your husband have many issue's to work through, and re-capture the love that was once apparent in your marriage. If the love AND respect are still there, even in small amounts, then you two have a great chance of making this work. A few things I would recommend for you, as the wife:
1) Be honest. Be honest with your husband, the pastor, and most importantly yourself. Only your honest feelings & emotions can resolve the issue's.
2) Don't expect your husband to be able to "read your mind". Tell him directly what you want to say, and do not "dance around" your words. That will create more problems for you, as your husband will misunderstand you, and you will get more mad at him for that :O)
3) Leave the "religion" out of it. Don't be intimidated by the fact the this person is a Pastor. For you, he is someone willing to help, and that's a great starting point.
That's it. Being nervous is normal, and it's part of the healing process. It's "embarrassing" to think that someone is going to know your most intimate troubles. But, in order for the healing to try to begin, you need to let that go and "not care" what their judgement is. You are not going in to be judged.
A pastor knows that IF you are there to work on your marriage, then there are problems. He will be prepared to hear "the worst". There will be no judgement on his part, and if there is, you will need to go elsewhere.
Try to leave the past behind, in order for you to work on your future. You are making the decision to forgive your husband, obviously, or you wouldn't be attempting counseling. Stick to your decision and fight for what you love.
Many blessings are sent your way.
~N. :O)