Chaunte, I'm far from an expert on coming out to one's spouse (seeing as how I haven't had one for 20 years), but I've had really good experiences coming out to family and friends (including my ex), and I'll pass along what I've found helpful.
Because all of my family live a great distance from me, I put most of what I had to say in a letter, then called and told them I was emailing it and to call me after they had read it. This is far from the ideal situation, but it did have a few advantages.
First, it forced me to sit down and really crystalize my thoughts on what I wanted to say. I was able to make sure that I said everything I wanted to get across, and by reading it over and over, to determine what I didn't want to say. I got my therapists opinion of the letter before I sent it; she made a few suggestions, and I incorporated about half of them.
Second, I knew that if I tried to say everything that needed to be said, I would break down more than once and it would be hard to go on.
Third, it eliminated interruptions. It was a way of making sure that everything was said, rather than leaving something out due to being sidetracked. It also eliminated the possibility of my getting cold feet half way through and backing off.
I'm not suggesting you just walk in and hand your spouse a letter, but I can see sitting down and explaining that what you want to tell her is really important, and that it's hard for you to say it without bursting out in tears (this will probably be true), so you've written a part of it out and you'd like her to read it. Tell her how much you love her, how important she is to you, and how afraid you've been to tell her.
I have no idea if this would work for you; you know your situation, and you know your spouse. Trust your feelings. Personally, I wouldn't want my therapist in the room at the time; it might make your wife feel she''s being ganged up on. She will feel vulnerable enough as it is.
By the way, if you'd like a copy of my letter, just let me know. Even if you don't go that route, there may be something in there that you would find helpful.
However you go about it, good luck! It's probably the biggest step you'll ever take, and probably the hardest. However it goes, just remember that there are a bunch of us here on your side.
Annie