I hate myself

21 years old here. I'm engaged to a beautiful and wonderful girl, been together for 4 years. Would be great except I'm starting to wonder about my sexual orientation. I've become interested in men when I had no interest when her and I got together. I wish I didn't feel these feelings, I hate myself for it. I wish I could just go back to being interested in just her and not wondering about "who I am." I'd rather kill myself than tell her I want to figure out who I am. I just don't want to fuck up somewhere down the road inside of a marriage. She deserves better than me, part of me wishes she never met me so she'd be better off but another part of me cherishes the memories I have with her. I still love her and I always will. I just hate myself. I know if I tell here that I want to figure this shit out I know it'll be over, she'll hate me, and my potential future of a happy marriage and kids will be destroyed. Fuck this is tearing me apart. I'm also sexually attracted to both sexes