Terene, as I mentioned in this thread before. I have talked to God about this very thing. I have never been convicted for MB.
My wife has multiple sclerosis and if we have sex once in a month, we've had a good month. I have a huge sex drive. For me the need is at least once a week, preferably more often. I MB to relieve that need so that I'm not bugging my wife for it.
I recently prayed and talked to God about my MB again and what I was given in response is not to think of other woman as that's adultery just as you metioned. However, thoughts of my wife are fine. She is my wife, is she not? Se's not another woman and as I have already said, one must have lustful thoughts in order to initiate sex within marriage. Generally, one is not thinking of butterflies and roses in order to get in the mood for sex.