Pia,
I sort of get where you're coming from, to be honest; and while this is totally something you need to work out for yourself, coming from my own experience, I hope I can offer some helpful words.
Whenever someone is first questioning their gender identity, the first thing professionals or individuals ask is about wether or not this is sexual in nature. Well-if trans 101 is that gender and sex are different things, then does it have to be either/or? Imogen Binnnie, a great transgender author, has a wonderful passage in her book Nevada (anyone who sees this post: READ NEVADA. IT IS AMAZING!) about how our kinks tend to reflect something about ourselves we've been trying to suppress. Sexuality is an area closely associated with the unconscious mind, if you believe the school of psychodynamics, and even if not there's still a lot of validity to the idea. If you spent your entire life repressing the fact that you were actually a girl, wouldn't it make some sense that this might emerge in sexual situations? If sex and gender are completely different things, then isn't it possible that this is both a fetish and a core part of your identity? I don't know what's inside your head, but just keep in mind that it's possible for you to be both a kinkster and a trans* woman. Sexuality and gender are different things.
Trans* people, like any other people, can be gay, straight, bisexual, pansexual, asexual, demisexual, sapiosexual, sadosexual-pretty much anything a person can be. And our sexualities should not be allowed to invalidate other parts of our identity. Guess what? Forced feminization happens to be something I enjoy. It's how I first discovered my identity. It's not a big deal, it's not some taboo fetish I'm living out by transitioning, it's just a fact. And it's also a fact that I am a trans* woman. And while I happen to hate my genitalia, if you happen to like using yours for whatever purpose, that's fine. There are tons of trans* women who enjoy their original plumbing-and that does not make their identities any less valid. Your sexuality does not dictate who or what you are, and anyone who says otherwise is subscribing to a very outdated view of gender and sexuality;
The medical community has been trying to pick and choose who is and isn't trans for the last fifty years, and even now there are still people subscribing to that school of thought. It's based on some very outdated assumptions about human sexuality, what causes a person to be transgender. It's becoming more and more of an anachronism in todays world.
So: Are you transgender? That's only a question you can answer-not the forum, not your therapist, nor anyone else. I'm not telling you that you are; what I am saying is that you perfectly well could be, and with everything you've shared, it might even make sense. Nobody has any right to tell you what you are or are not on account of your sexuality, and if you would feel more comfortable as female, whatever that silly word means, then what you like to do in the bedroom should have no bearing at all on things. At all.
Hope this helps!