How do u know if he's the one?

Hey guys, so my boyfirend, he's perfectly what I ask for a boyfriend. He's kind sweet and all. But you know there's this feeling of needing the certainty that we're actually meant to be. I mean I really don't wanna lose him and experience love with another person, I feel like he is the one I can truly love and I do love him. But I'm asking you ladies whom started off dating and found the one and got married and are living happy life with their husband. How can you know if you can actually invest in him ?