How do you get over someone you're completely in love with?

I’m totally in love with my mate. Were quite close and are always messing around and flirting constantly. He didnt know that i liked him until my friend went behind my back and told him. We talked it over and he said that he thinks we should just stay friends for now. And then I find out that its because he likes someone else. I really really like him and i had thought he liked me, but obviously i was wrong. What do I do now? How do I win him over. I know it sounds stalkerish but we’d be perfect together. I love him, and i think on some level he might like me.