Started sometime between 8 and 12, depending on how you define it.
I'm 24 now and work at a startup, I had a similar experience to yours, except I dropped out my first quarter of school.
I've changed a lot since 18, I can say that much.
I honestly believe that if you took someone totally naive to programming and put them through an intensive CS + programming apprenticeship, they'd be a better programmer than me in 1 or 2 years easily.
I'm 24 now and work at a startup, I had a similar experience to yours, except I dropped out my first quarter of school.
I've changed a lot since 18, I can say that much.
I honestly believe that if you took someone totally naive to programming and put them through an intensive CS + programming apprenticeship, they'd be a better programmer than me in 1 or 2 years easily.