As you probably know, when you are attracted by people of your gender you cannot “transform” yourself to be only attracted by people of the other sex. Even if you try to ignore it, you will always feel this attraction. If you are not attracted by people of the other sex at all, there are some significant chances that you will never be.
In your message, you write your son seems like you were when you were kid. It is normal that he sometimes reacts and does like you did because you raise this child; you are his model. However, it isn’t mean that he is homosexual because he has some “girly behaviors”. Trough our development, we learn how to act like a girl or a boy as the society want it. Nature hasn’t made all the male attitudes and female attitude that we now know; nurture made it. I don’t know what “girly actions” your son does, but I know that gender identity has nothing to do with sexual orientation. If your son clearly mentions that he (she) IS a girl, it is more about what psychiatrists call “gender identity disorder”. In other words, maybe he(she) borned with the wrong sex (a female in a male’s body). I know it can be hard to understand, so I will give you some information internet sites at the end of this message.
Before concluding your son is homosexual, heterosexual, a boy or a girl, it may be very helpful to give some time to you two. The only person who can know it is your son himself. Even if you try to scared him, it will not change what he is. Letting him understand what he is and how he identify himself can be a great solution. The best thing to do is to be respectful and openminded with him and his identity.