I feel you!
That sh!t happens when we're not looking. lol
Creeps so slow... you don't even notice it. Until oneday the feeling of being so (as funny as it sounds) unsexy thus powerless, bugs too much you have to take notice.
At least thats how it felt w. me, in my last relationship. (when that happened)
My suggestions would naturally be... break some of your behaivors w. her.
Change sh!t up. Throw her against the wall and take her like you never have before. Go down on her for ages, flip her over and spank her ass cheek harder than you ever have. Rub your hands up her back, pull her hair back... then fvck her in the a$$. lol
Sh!t like that, as far as sex goes. Change sh!t up.
I know when I'm in a LTR the sex naturally starts to fall into the similar patterns. Throw a wrench in that sh!t from time to time. I know we're lazy fvcks... but the electricity it pumps back into the interaction of the relationship is well worth it. Brings back those exact feelings you described. "Sexy, Mysterious, Dangerous"
Outside of the bedroom. Try doing dif. sh!t w. her. Like going somewhere random. Sneaking into a hotel's pool, late at night and skinny-dip. lol, whatever. Just start shattering the mold of "adorable, stable comftorable" guy.
Things were getting too predictable w. this 1 chick I was with. Too polished, cool. So oneday I took her to a second hand store, and told her to pick out the most insane, ugly, funny outfit she could. I did the same. I then took her to this pretty nice/cool restaraunt. You could imagine how it went. lol, it was fvckin hilarious. She loved the fact that I made her do that. She could ride on my strength to do something she would never in her life imagine being free enough to do. It was fun as hell, RANDOM as FVCK, and totally threw a wrench in everything she knew about me.
Needless to say... I then took her home, toar those fvcked clothes off, and ravaged her in a knew way. I know to this day, she still will remember that day as something incredible in many ways.
Break the routines. Fck w. her, but in positive, mysterious, adventurous ways.
Take her into an old rundown house, out in the desert... and fvck her. lol
It'll be scary... w. crazy/wild energy, etc.
Send her a silk red thong at work.
Wake her up at 3 in the morning, and tell her theres something crazy happening outside... come see! Then when she asks... "what is it?"...hold her hand, look her deep in the eyes w. seductive cheeky love, and say, "Me fvcking you underneath the stars."
lol, whatever.
Blow her off for a day or 2... then next time you see her, grab her in insane passionate lust. Kissing her like you never have before. And take her in heartbreaking desire. She won't know what the fvck hit her. Rest assured she'll be telling her gf's later on, she doesn't know what the fvck has gotten into you, but she loves it.
Bottom line... you have to reclaim that sexy unknown factor.
Break your routines, mix in some new behaivors, plan some random adventures.
I think you feel me.
SuaveOn'