Well I'm not a preachers wife, But I also know what you are feeling now and where you are coming from, because I myself am going through it too..
Here's my story.....
I have been saved and walked with the Lord since I was about 9, But I never really walked the walk of faith and really started to apply the word of God and search for him up until about 2 years ago where at that time I really just got set on fire for Jesus and was totally devoting my life to him me and my hubby was even thinking of going to seminary ourselves.
And then one day my mother in law was over and she told me that the reason me and hubby havent had children was because of her, because she prayed. And let me tell ya, that messed me up so badly I cant even begin to describe. I got it so deep into my spirit where it was all that I mediated upon, and no matter how hard I tried I could not get it out of my thoughts. It got to the point as time passed that it had me questioning my faith.
My theory is I think when there is a call on your life or your spouses life etc the Devil knows this and he wants to bring us down and attack us. He will do everything in his power to try and pull us down and keep us defeated. There are many stories of preachers wives getting sick or being depressed and it is all just an attack of Satan to keep the ministry from sucess.
I would suggest Deliverance there is a website
WWW.DEMONBUSTER.COM it has lots of prayers for protection, because I think that this is what it is a attack.
I hope I made since I know I ramble alot lol But hang in there it will get better.
Take Care