Is it normal that i have no idea if i'm a lesbian, or straight, or asexual?

Ok, I'm an 18 year old girl and I'm very unsure about my sexuality, even though I tell people I'm straight.
I've always had crushes on guys ever since I was a kid, but I never wanted to kiss them or have sex with them. I only kissed one guy in my life, like 5 years ago, it was really lousy.
Anyway, I think I have a really low sex drive, but when I watch porn, the only thing that turns me on is the woman! Especially watching lesbian porn.
I don't picture myself on a relationship with a woman (I think it'd be weird), only with a guy. I imagine myself hugging or cuddling in bed with a guy, but never kissing or having sex (I don't think I would enjoy sex at all as I would with a woman).
And when I was 13 I had this HUGE crush for a year on a (female) friend of mine.
Sorry for the bad english, it isn't my first language.
So, what do you think about my situation?
(I know that I'm the only one that can truly know this, but I'm completely confused and I'm very afraid to talk to anyone about it, so I'm asking for your opinion)