How do you know if you're in love?

I've been having a feeling that I'm In love with this kid that I've been talking too since my freshman year of high school. I don't know how I can tell, or if it's just my hormones or what. I'm gonna be a senior and he's graduating this year and he says he wants to see where things go after he graduates because he might not see me anymore. Should I confess that I feel like I'm in love or just let it go? & how do I know I'm in love.. Help. ):