I need to get something off my chess for so long, seems like the right forum to do it.
We've been happily married for over 20 years, no issue with family, no issue with kids, no issue with sex but I have an issue of my own.
I would say that our sex life is better than good, she's always satisfied and I am as well for the most part.  What I mean about "for the most part" is that I enjoy everything we do, including giving her oral pleasures; however she just flatly refuse to perform oral sex on me, even after 20 years of marriage, she viewed it as disgusting (although she enjoyed it when I perform it on her).  I used to enjoy it a lot with previous GFs before I met my wife but cannot convince her to just try it so a few years ago, I always feel that something is missing so one day I went to see a prostitute to get oral sex.  Ever since, I see prostitute probably 3-4 times a year just to get the pleasure of getting oral sex. 
I have tried again and again to ask her to try it out, but she seems to get more upset each time so I stopped asking and continue seeing prostitutes.
I feel bad as I view this personal pleasure is cheating on her, but I can't help it because she just doesn't satisfy me on this 1 thing.  Each time afterwards I feel very guilty and promise to myself to stop, but after a few months, the urge comes back and overcomes my moral voice. 
I know for sure I can't talk to her about it, she is a very strong minded person who had several time ensured that I got her message loud and clear "if you ever cheat on me, our marriage is over, end of story, I won't listen to any excuse".
What can I do? I have a weak, weak mind.  javascript:replaceText('%20::confused::',%20document.forms.postmodify.message)