why does gay exist?

This question came across my mind when I'm every time when I'm surfing on the net(internet in this case).


WHY DOES GAY EXIST??


WHY DOES SOME OF THE MEN GET ATTRACTS TO MEN BUT NOT WOMEN??


Well,  I can tell you that is not we choose to be gay(or maybe yes for some case?) or the the environment we grew up with.
From what I heard,
it could be some hormone changes to the baby when the mother is pregnant.
What makes the hormone changes?
It could be the supplementary pills that the pregnant mothers taking when she is conceiving the baby.
some of the supplementary pills cause unbalance hormone to the baby.
Ok. Let say that straight men has about 90% of testosterone and 10% of estrogen.
but those pills that pregnant lady taking might cause some changes to these hormone which will mess up the sexual preference of the baby. in short, GAY/LESBIAN!
As you can see right, there is some guys who act like girl vice versa to the girls. 
Well I think this explained that.
I don't know if this the reason of men become gay or not, but I personally believe that this has something to do with the gay out there.
CHEERS!