Oh yeah, I wanted to second others' comments that nobody ever feels grown up! It just doesn't happen. And you're certainly not going to feel like an adult at 17, though you may feel that you're more mature than others your age. (It might be true, too.)

I don't think you've wasted any time. Experience is always useful, even when it's painful. And you're taking some exciting steps forward now.

I think it was novelist Flannery O'Connor who said that at five years old, we've already got enough material for a lifetime of novels. Your early experience means something. You never know when you'll be able to use it. If growing up means forgetting our early trauma, then it's not worth it. Nothing is lost!