I'm very scared of growing up D: please help!?

i'm 15 and i'm going into high school, my moms a teacher at that school so i know the responsibilities of high school, leading into collage. i also have a boyfriend that i've been dating for 4 months, but we've been talking for a year. we're starting to get into talking about our future, we've picked names out for our children, we're planning on having them when we both have stable, good paying jobs, i want to be a psychologist one day, and he a vet. my life is moving so fast, and i don't know if i'm ready to get older, its very scary. i know i'll make mistakes, and i know its not going to be easy, but any advice would be great!