Advice (I need as much as I can get).

Ok guys, for second I need you to do something for me.
Before you read this I want you to forget my age.
Forget I'm about to be a 15 year old freshman in high school. Forget it, that way I'll get honest answers.

I need to know how do you know when someone is the one.
You know, The One.
And I think I know. I mean, I know but thing is we aren't together. But I know it doesn't matter if you break up as long as you come back and thats what I want to know. I want to know signs that he'll come back.
Like, tips.
Like, if he does this than maybe.

He loves me, I know that.
He let it slip again today.

I just need help guys.

Thanks.