It is a personal decision. Somewhere down along the line sub-consciously most likely, your body decided to like men. Just because your gay and you are attracted to male phermones doesn't mean it's a product of nature. It's a product of your mind. The human brain is capable of far greater things than being attracted to same sex phermones.
No one is born gay or lesbian. Just like no one is born with alcoholism. We're a clean slate when we spring from the womb just as we have evolved to be. And we have evolved to reproduce. It's basic animal instinct. To survive and make sure our species continues on.