I think I might be aromantic or asexual or both. I considered other options but settled on these two because when I think about it, I never had a crush. I never thought about having sex, because i don't like the idea of it. I never even been in a relationship. I'm not sure if I just never had a person I am interested in, or if im unable to.
At your age, it would not be at all uncommon to have no interest in sex, not have a crush, and not be in a relationship. It's unlikely you're asexual, and there's no credible evidence to support a separation between sexual and romantic attraction/orientation, which rules out the 'aromantic' part. So the most likely outcome is that you simply haven't gotten to the place where arousal and attraction have kicked in yet.
It sounds like you have been doing quite a bit of reading to arrive at the idea that you are aromantic or asexual, but I would caution you about what you read concerning these two labels. I'm afraid there are some very outspoken people who have completely redefined what it means to be asexual and have done more harm than good in propagating misinformation on the internet. You are still young and there is plenty of time for your feelings to develop, so don't stand behind the banner of asexuality just yet. In the months and years ahead things may very well change, but it will be more difficult to embrace those new feelings if you have committed yourself to the idea that you are asexual or somehow lacking in attraction to others. Stay open minded and give yourself time and space.
I have read thousands of comments here and on other websites of people that say they feel sexually attracted to one/more gender and romantically only to the other gender. I assume they are all in denial, or lying according to you and your scientific evidence.
Are you really going to argue that a 13 year old is asexual? Please don't talk about stuff you don't understand, or don't have complete info on. Staff can see things you don't. As to the issue of sexual vs romantic orientation, "romantic orientation" as the small-but-vocal contingent describes it is basically "I feel a strong sense of connection to this person, but have zero interest in having sex with them." There's a phrase to describe that sort of connection people feel with one another. The phrase is hundreds of years old, and is called "emotionally intimate friendship". It has nothing to do with sexuality or sexual orientation.