How do you know he's "The One"?

Ton

I have been with this boy for 2.5 years and even early on, we started talking about a future together. We have grown a lot and he's my pillar at all times.

I'm just not sure if it's too early to get settled on a person.

I'm 20 and he's turning 21 this year.

How did you know? How did you know your boyfriend was THE one?