I need some help.

Obviously I am a stupid idiot. I have to confess. I had an five-year affair with a colleague (I am single, he has family). In the end of last year he turned me in (to his family) because we did fighting for some reason. Then it seems everthing is over. The guy is screwed by his wife, in the past several months his wife (japanese housewife, 7 years older than the hu*****and) never stops fighting with him, but claimed cannot live without him, although the poor guy is already kicked out of his house. I have never thought I would marry the guy, so I have never told anybody about this, for me maybe just for pleasure (laugh). At beginning I felt guilty to the family, but after the wife blocked my way on the way home, played theatre (shock, scream) in front of my door, followed me all the way home after my working, I become cool. Now the lady has the idea--blackmailing, she wants 300008364; from me for compensation, of course after she gets the money she still lives with her hus. If I refuse to give the money, she still goes on her show forever, she claims that she will tell my other colleagues (a big threaten to her hus.). What should I do now? I need some advice, although I knew I was completely wrong.