I think I'm in love with my best friend....

Ok so I need some outside perspectives on this situation. Last year (my freshman year of college), I met a guy who I developed a minor crush on. We became close friends and he knew I liked him, but he told me he didn't feel the same. The crush went away and I moved on, but a month later, the feelings came back. He's my best friend on this planet and we know each other better than anyone else. He has a girlfriend, but he told me he goes back and forth on whether he really wants to be with her and that I know more about him than she does. She even comes to me for advice about him because she said I know him better than anybody else. I told him what kind of girl he deserves over the summer (basically by secretly explaining to him how I feel without using my name) and he told me that's exactly what he wants in a girl. And then I showed him a poem I wrote about him and he said that if he ever found a girl that felt that way about him, he would marry her on the spot. Everyone thinks we're going to end up together somehow later on in life but he always jokes about how I "used to" have a crush on him and how it'll never happen. It hurts me a lot inside and I've tried to date other people but somehow it always comes back to him. I recently actually dumped my boyfriend because he told me he didn't like my best friend and he didn't want me hanging out with him anymore. I will always choose him over any guy I ever date, which scares me because I know it'll be hard to find a guy who is ok with my best friend being a straight male. Can anybody share their opinion of this situation or give me advice about how I should handle this?? I'm really torn because I can't lose my best friend but I also know I'm hopelessly in love with him. I know I need to get on with my life, but there's no doubt in my mind that he's the love of my life and that we're meant to be with each other.