I've grown up being told that I'm very intelligent, and that I can do great things (just like any other kid I guess) but when I look at my scientific heroes and how young they were when they started their path to greatness, I feel like it's too late for me, and that I will never live up to my family's expectations. I know I'm not dumb, but whenever I struggle in math or science class, I wonder,"Did Neil Degrasse Tyson or Carl Sagan ever have these problems in High School?" And then I just end up feeling like a loser who will amount to nothing. I'm also worried that being female will drastically decrease my chances of success in the scientific field. Are these fears normal??

Also, stop comparing yourself to other people, it's pointless. To me, those two things are what might prevent you from becoming successful. Of course you'll make mistakes, who doesn't?
Sometimes success isn't about things you can control. Look at Clyde Tombaugh. Although he discovered Pluto, he didn't have a chance of finding Makemake. He was in the wrong place at the wrong time.
Nobody can guarantee success. But what you can do is prepare for it, and also give yourself every chance. The only way you'll guarantee you are not successful is by giving up.
You may not be the next Marie Curie but if you are not, don't let the reason for that be something you did (or didn't do).
I walked out of university and into a menial job. I am convinced I could have been a research mathematician, but I threw that away.
However anything less than relentless, and your odds start to drop rapidly. There are billions of people in the world and only a handful of famous names in whatever field you aspire to.
That is not to say you cannot have a very happy life, you need to get a roof over your head as a priority and then do something career wise interesting and meaningful, its nice to feel you are making a difference and contributing. I think this can be achieved clearing blocked drains as it can be discovering a new scientific breakthrough.