Think of it like this, you are only straight by default. When it comes right down to it, it just matters who you like more, men or women.

In ancient times having sex with another man or even a young boy was not looked at as homosexual or anything like that, it was all about the penetration, dominance and good feelings. Somewhere along the line making love with a partner of the sex was looked at as weird and gross.

Personally I don't get aroused by men, so I am not gay. If sex with men makes you happy, then go for it and trying to fight those feelings will make your life hell. Regardless of what the majority of our society may think homosexual sex is as natural as masturbation.