In love

So I'm crazy over someone, and currently we're only friends. We've dated before, but he got interest in someone else. I can't live without him, but he doesn't believe I truly love him. He does have a girlfriend. He told me find another man 1000 times better than me and you will live a happy life. I think that he's just so humble, but he thinks he's a bad person. But if I really love him, how do I get him to realize that it was love at first sight?