Not Just Another Pimply Face
I've loved my fiancee deeply for her intelligence and beautiful personality since the day we met five years ago. However, I don't think I was ever really attracted to her. In fact, lately, I'm increasingly repulsed by her. I hate her slouchy, tomboyish walk, and I'm turned off by her unfeminine manners. She constantly has pimples; her breath smells; and her lips are always dry and chapped. I go through the motions with her in bed, but it's become very unsatisfying. In all fairness, she has a great body, beautiful eyes, and a beautiful smile, and I really do love her and feel absolutely horrendous for sounding so superficial. I could never actually cheat on her, but I've been having thoughts of it, and that alone makes me feel terrible.
In any relationship, there's an inevitable erosion in hot and steamy, but you're with the wrong woman if your sex face could easily be mistaken for your standing-over-a-septic-leak face.
Okay, so your fiancee could win inner beauty contests, but beauty on the inside just isn't enough unless you've been reincarnated as an endoscopy camera and sent on safari down her digestive tract. Then it wouldn't matter that your favorite thing to do in bed is roll over and realize she's away on business or that your sexual fantasies involve picturing her fully clothed, scribbling out a purchase order for a warehouse of zit cream.
Looks are especially important when getting into a long-term relationship (especially the "till death do us part" kind), because if you're careful crossing the street, you'll be spending a really long time looking at the person. The ultimate in well-intentioned cruelty is marrying somebody you aren't attracted to and will come to despise as you find her increasingly physically repellant. You should instead figure out what your "type" is and only get together with someone who fits solidly into it. We all have a type -- looks, smell, and behavior we're drawn to. For some people, it spans a broader spectrum of humanity (and in some cases, farm animals). For others, the range is smaller, which is fine, as long as they accept that they're narrowing their options -- and don't narrow them so far that the only woman they could ever go out with is Jessica Biel.
The least hurtful thing you could do now would be to hop a bus back in time and sleep in on the morning you met your girlfriend. Barring an ability to bend the laws of physics, you should break up with her immediately. (Tell her the relationship just isn't working for you anymore, not the whole ugly truth.) When you love a woman you aren't also in lust with, you should resolve to love her only as a friend -- same as you would some loyal hairy guy you know who's also "beautiful on the inside." Nothing comes between the two of you, either -- save for the feeling that a roll in the hay with him would pale in eroticism to a roll in a river of cat vomit.