Should I tell him I like him and how should I do it?

We've known who each other were for 3 years now. But we just talked this year. Well, we talked before on myspace but that doesn't count. This guy is seriously my soul mate. He's everything I ever wanted : tall, tan, buff, dark chocolate brown eyes, curly brown hair, puerto rican, nice, funny, compionate, sensitive. He's sooooo dreamy! Anyways. Lol. He always flirts with me, every single day, he asked me for my number, he friend requested me on facebook, were like really good friends. There's one problem, he has a girlfriend. They've been dating for a month and a half. He never mentioned her to me though, I found out from other people. He doesn't even stick up for her because this other girl in our cl said she's ugly and a B*tch and he said nothing. But yeah I want to tell him I like him but I'm so scared of rejection. Help?