with cousin's wife, now she's pregnant with my child........?

You need to tell her...just her for right now. If she has any doubts after baby is here, take a DNA test on the down low. If its yours, then well, gotta face your cousin. If its not yours then I think keeping the little "one night affair" a secret would be best. Just because it will cause problems and why bring a baby into that. I know it hurts... believe me I understand better than you think. Of all things Im pregnant by an ex's twin brother. ( yea I know) Be carefull and good luck.