Is it normal for a straight guy to watch gay porn? if not why? and why do some guys think about other men sexually when straight?

Bisexual attraction: The guy could be bisexual -- erotically attracted to both women and men. Most people are at least curious about porn, but don't watch it repeatedly. Watching a lot shows some attraction to it, and preferring a particular type relates to unconscious, innate erotic leanings. There may be confusion as different types of attraction sort themselves out in adolescence & early adulthood.

Yes, I think so.: Hoping there're other answers too. Especially for guys as young as you - with strong, fresh sexual energy - anything of sexual content can be very attractive. I'd hope you avoid hurtful, violent and demeaning content, but otherwise - all is fair (in moderation, of course - addiction is bad - and you need a well-rounded life). Reasons? To learn about it, to evaluate yourself, because you may be bi.