Hi Lora... good topic!
I am a transitioning TS, but for years (going back to some of my earliest memories) I have known I was female, and dressed accordingly when possible. I never thought it would be possible for me to transition, so dressing the part in private was my only outlet.
After reaching puberty there was of course a sexual component to it, but it was never the point of dressing. I was becoming a sexual person and as I knew I was female, my sexuality was strongest when I was expressing my true gender.
Over the years dressing became more and more a part of my life, as my despair at having to live as a male grew stronger. Sex remained incidental, and even when I wasn't dressed, my sexual fantasies were those of a woman. In my relationships I was, in my mind, female.
Now that I have finally begun to transition, clothing still plays a big part, although in ways different from before. Prior to realizing that change was possible, I tended to dress in an ultra-feminine manner, compensating for my hated masculinity. As my transition progresses, I tend to dress more casually, with the more feminine look reserved for special times, like going out clubbing, or meeting friends for Sunday brunch.
The necessity of dressing as a male at times has become horribly depressing; I am still working as a male, and spending 10 hours a day 5 days a week that way is getting to be more than I can abide. I try to make it a bit easier to deal with by wearing all womens clothing, even in male mode: jeans, sneakers, and tops that are androgynous enough to get away with. I'm hoping that won't be necessary much longer.
By the way, if it matters, my orientation has always been toward women, although I have to admit I have recently begun to see the appeal of men. Well, some of them, anyway!
Annie