holding on to people that only live in your heart and memories

I have fallin into a rut recently...I started talking to old friends from my long ago past...one in perticular...Eric...My very first grown up broken heart was at the hands of this man....but that was long ago...I believe I was 17 or 18 at the time...He was kinda famous...and of course married...but at that time I had no Idea how wrong it was for me to be inlove with this man....we wont go into such details as to mention last names, there could be too many reprocussions for me to do that. The Problem I'm having now is...well I never really got over this man....and it has been20 years! The other big problem is that I have been engadged to another man for the last six years...Dont get me wrong,,I love my fionce...he's a good guy...and tries real hard to make me happy, but I find forbidden pleasure in a simple note from this man...and my fionce deserves much more than what I have been giving him lately...and he damn sure dont deserve to have me going behind his back and emailing an old flame....He knows That I talk to old friends on fb...some of those people are people that link me straight to Eric....and my fionce knows that...I've never kept how I felt Eric a secrete...only the part about how confused I am now...what in the world am I gona do? what would any of you do????