Hi- You probably know this, and this is basically when Jenny described, but it is classified as a mental disorder to be a "Girl trapped in a boy's body"
Do you feel that way? Don't be afraid to be who you are. If you feel like a girl, then you're a girl who's had the misfortune of being born as a male. There's a movie about a girl (born a boy) named Gwen, (a lifetime movie, where she was tragically murdered) and in that movie, there was an organization involved with Gwen for gay and transgendered people, she explained a theory out there that helps explain why some people are transexual. In the womb, we all start out as girls. Eventually, the boys develop into boys. It is theorized that in this process, your mind remained a girl, while your body developed into a male. . .
Anyway, to figure this all out it is necessary to o to a therapist. A friend of mine has a cousin who was born a male and lives with him, She wanted to be a legal female, but didn't want to go to a therapist, but in the end she decided to go, and she was diagnosed, and is now legally a female. Unfortunately, growing up she was highly discriminated against. I don't want to scare you or anything, but when she was in high school, she was just assuming her role as a girl, and a group of guys (who are cowards and shouldn't even be called guys, more like beasts. I would call them dogs, or pigs, but I love dogs and pigs too much to demean them like that) beat her up after school, and took her clothes, making her walk home that way. The school refused to do anything about it. Needless to say, today she is very sensitive about her identity and her past. I'm just telling you this so that maybe you can see the importance of realizing that you are a girl- 100% a girl, but that you have had the misfortune of being born within the body of a guy, but still, you are a girl, and that's okay. Love who you are, and be comfortable in your own skin- that is the best thing you can do for yourself. As for your dad, Technically, you're not gay (unless you like girls) although that fact may not soften him up right away, he will get over it eventually. The fact that he brushed it off and didn't go off, might suggest that he's known all along- that he's noticed it since you were in diapers, and was hoping that he was wrong. Now that he see's he was right, he's hoping if he ignores it, it will go away. But he will get over it and accept it one day.

I hope this has helped.