Congratulations to you for finding what it is that you truly love to do. And don't feel like you're not settled simply because you changed your mind. It's worth it - and it's much easier - to take your time to try out new things now rather than sticking with something that you're not sure about and then suddenly realizing when you're 35 that it's not for you. Trust me.
My trajectory: I entered college a pre-med biology major, was miserable, discovered I liked literature, majored in English, worked in publishing for 3 years but started contemplating grad school in English after 3 months in the "real world," realized that I liked French literature much more than English-language literature, and went to grad school for French.
For 8 years, I plodded very, very slowly towards my Ph.D. because I couldn't decide if teaching college was worth the misery (and the money!).
In my 8th year of grad school, I got a full-time job teaching college and knew I'd found my passion. I wrote my dissertation in 2 summers and finally got my degree after 10 years. I was 35.
I finished paying off my student loans in 2011, when I was 45. But I absolutely love what I do.
I've known plenty of people who've made career changes after they started working in the field they always thought they'd wanted to pursue. So...finding what it is that you love to do when you're 20? You've got a huge head start!
And even if you change your mind 10 times in the next 10 years, there's no reason to stress about it. As long as you ultimately end up loving what you do, it's all worth it.