I've done quite a lot of thought about the subject of crossdressing and sexuality. It's really one of the most misunderstood variations of human sexuality I know. It's not only misunderstood by the public at large, but often by the person involved. For many it's considered simple fetishism, though I've firmly decided it's much more than that. In recent times we've seen greater understanding and tolerance of gays and lesbians, but not as much for the sexual aspects of crossdressing. But being gay is, essentially, about sex-- it's about what turns you on. There's nothing wrong that. I believe the same can be said for the sexual crossdresser, which should be recognized as just as valid a gender minority and lifestyle.
There is what I believe to be a flawed clinical term for male-female sexual crossdressing: autogynophilia. I think a more accurate term might be autogynosexual. Unfortunately for us, autogynosexuality is not as easily understood, nor is there any clear lifestyle model as with the other sexual minorities. We kind of have to create a lifestyle for ourselves.
A lot of other people share similar fantasies to yours, but fantasies tend to vary considerably from person to person. How you deal with and manifest yourself sexually will, in the end, be something that's entirely up to you. I believe, though, that you'll be a much happier person by doing so than by trying to adhere to an off-the-shelf lifestyle and conform to any assumed societal norm.
~ Lyric ~