Dear Wife,
First of all, how old is your sister? How does someone spy on someone in the shower with a spoon? How reliable is sister's word? Could she be making it up? Maybe, your husband was sexually abused as a child, that doesn't meant that he has problems. I'm not saying that he does, but I want you to look at all the possibilities here. IF you husband admits doing it, OR you know that he has exhibited the symptoms of "sexual addiction" before, then he needs counseling, now.
Second of all, do you have small children that need to be protected from him? The "sexual offenders" that I worked with that didn't get help or counseling, usuallly "acted out", with their children, nephews, neices, or neighbors children.
Yours is a very serious problem! Please, don't be in Denial about what may be happening in your home!
If you have small children to protect, which a lot of "sexual offender" do, because they usually live with or marry women with children that can be their "potential victims".
No, I am not saying that your husband is a "sex addict" or a "sexual offender", but IF he is please.....don't continue to live with his sickness, insist that he either get some help---or LEAVE.
God loves you and so do I, Sally B. [Richmond, TX]