but I would say that you need to have a good think about how you really feel before you decide to tell her anything. Is it just a phase or do you really need to express this part of yourself? Is it something you can introduce into your existing sex life or do you feel that you'll have to go elsewhere? As you point out it may very well end your marriage - is that what you really want?

I'm probably not helping as I'm sure you've already thought about all of this, but if it's just a fetish thing then it's up to you how much importance you want to give it. If it's the only way you can get off sexually now then you probably will have to tell her eventually.