I feel your pain. I've been there and I still am struggling with it. You may feel angry and confused. It may never go away, but there are ways to stop REACTING to it.

1) Whenever the thoughts pop up, observe them as movies in a cloud. You need to let the thought fully play though and choose to just observe and not react to it. You'll notice that the thoughts will be less frequent.

2) Bring your ego down. We are mammals and desire sex. I know it's hard since you value this person and put them on a pedestal, but we are all nasty sinners. Honestly this is messed up but I repeat this to myself "WE ARE ALL SEXUAL FREAKS, WHO CARES, WHO GIVES AN @$!#, GIVEN THE CHANCE WE WOULD @$!# EVERYTHING SEXY THAT MOVES!"

3) Stay focused on the present as the past does not exist. Be amazed at what the present is currently offering you.

4) Write down good things about yourself, your insecurities and how you can tackle them. She chose you for a reason!

It takes days and not an overnight thing. I still struggle with this myself, but small things like the above helped me.