As I see it, you have 3 options...
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You can notify this new subbie of the problem, and tell him that you cant dominate him.

or

You can be honest with your husband, and throw caution into the wind.

or

You can get over your guilt and lead a double life.
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Now you didnt mention if this relationship was serous.

If its just play, then you can continue to play, and then change your mind later on...

...But...

If it is serous, or becomes serous, then you may want to change your attitude.
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With that said, I am not the one too make up your mind, for I only want to offer you my personal opinion.