Im falling in love with my best guy friend.?

We’ve been friends for so long (11years) and I’ve only started to realize it but I’m falling in love with my best guy friend. He makes me laugh and smile and I love spending time around him. We aren’t really awkward about physical contact with each other but it’s never been anything “romantic”.He also has a girlfriend. He mentions her sometimes and I get jealous but hide it and pretend to listen. I tell myself to remain platonic but only because I fear losing him as a friend altogether. Do you have any advice on what to do? Thanks

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