[Kizzy]

Pervert.
1.
to affect with perversion.
2.
to lead astray morally.
3.
to turn away from the right course.
4.
to lead into mental error or false judgment.
5.
to turn to an improper use; misapply.
6.
to misconstrue or misinterpret, especially deliberately; distort:
to pervert someone's statement.
7.
to bring to a less excellent state; vitiate; debase.

If you are deliberately misleading your spouse as to your fidelity then I'd say that the term 'pervert' was apt as to your intention...