Hi KG. As others have said, you're a girl in a guy's body. That's it.
So you're a girl and you're sexually attracted to men, so your straight. And I'm a woman who's sexually attracted to women, so I'm lesbian. It seems there's a fairly large number of transwomen who have felt the way you do, and a lot of them spent years struggling with their GID and sexual orientation at the same time. At least until they discovered, or admitted they were transgender. Since I never went through that mental maze I can't judge you or anyone else who has to rationalize their own transgender and gay issues while avoiding stereotypes. But I could talk for hours about being a transgender monogamous lesbian. (Hint - not much fun with a wife who's not lesbian.)
Hey, at one time I thought "Maybe I'm gay", but I wasn't attracted to men so it didn't make scense. And so I really don't know how you feel, and I'm not going to try and guess. All I can tell you is maybe you don't need to worry about sexual orientation right now since transition is going to change everything about how you view yourself, and how others see you. You know, "gender and sex are not the same", but they can both screw with our lives at the same time.
Hugs