26 M Engaged with no one to talk to...

I know that I have been attracted to my same sex for quite a long time. In all honesty, I have had these feelings and attraction towards dudes for pretty much as long as I can remember. I have been with a few men from time to time but no one has really caught my attention for more than a month or so. I had a boyfriend before my fiance and I got back together back in 2014. We were former sweet hearts back in high school. She in many ways was my first love and we have made some wonderful memories together. Before we reunited, I have been on and off with men, then a woman or two, and then back to dudes. However, for the length of my current relationship I have been looking at mostly gay porn, and I find myself fantasizing about men more than women. But, I absolutely love my fiance! And in the past we have had great sex and established a quality and loving relationship. It rips me up on the inside knowing that I will destroy her mental health, ambition for the future, and buckle her financially if I pursue these feelings of mine. I aspire for another guy like me. I appear completely straight and enjoy being masculine. Ironicly, my fiance is a tough woman and carries similar masculine qualities at times. However, she has a temper and I am losing physical attraction to her and feel like she is taking my individuality from myself. But I love her, I can't stand to wreck her! Then again, I feel like I'm destroying my own identity... fuck, idk what to do...