The 'Keeping Up with the Kardashians' star, who celebrated the milestone birthday in August, insists she is in no rush to grow up despite her sexy image.
In a post on her newly launched website, she wrote: "It's funny when I think about how people see me. Everyone thinks that I want to be older than I am, that I've been in some huge rush to turn 18. But in a weird way, turning 18 was kind of sad for me. Sad, but exciting at the same time; it's a milestone."
Kylie, who is dating 25-year-old rapper Tyga, has no plans to become a party girl.
She added: "I feel like people are also expecting me to just go wild now, as if I've been holding back. But I'm still the same girl that I was the last month, when I was 17.
"I'm still growing up, learning and making mistakes, just like any other teenager would, yet millions of people are watching and judging me. That's the part I don't know if I'll ever get used to."
The blonde beauty, who recently moved into her own home in Calabasas, California, also admits "now there's a whole lot more responsibility that goes along with life" after years of being "the baby of the family."
She wrote: "People are expecting more out of me and that's overwhelming and nerve-racking."