Way back in February a user of Rateen, an online message board for gay Korean teens, asked this question and got what I think is a spot-on answer. You can read more about Rateen and how it got started in this article on Lesbian Park, which includes quotes from the site’s founder.
Q:Is there any way to tell for sure if I’m gay?
A lot of parents ask this kind of question.
If their son or daughter announces they are gay they get nervous and start thinking, “I can’t believe what my child says now. I must have made some mistake or misunderstood something,” and start looking for a way to tell if they are gay or straight.
Recklessly, some confine their children to mental institutions or send them to a psychiatrist for counseling.
First I want to say that that is no way to go about it.
Straight people don’t have psychological problems just because they encounter mental or physical difficulties, and the same is true for gay people.
So there is no psychological test or method of counseling which can tell you who is gay.
There is nobody but yourself who can say if you are gay or not, and you just have to see where your own sexual orientation points.
Judge according to which sex you feel pulled towards.
Sometimes some psychiatrist will claim to have a homosexuality test, but it is just something individual to each person.
Right now it seems like there’s no academic authority who can confidently make a diagnosis, and according the American Psyschology Association attempting to do so is a mistake.