I know it's been asked a million times, but what do I do if I'm gay and I'm in love with my closest friend?

It's all about being true to yourself and remembering life is short and being open about your true self is so important because you have to live life to the fullest. If you get rejected it may feel embarrassing at the moment but truly it is something everyone has or will experience. They are your closest friend for a reason and you should trust them. If they end up rejecting you that is okay, you remained true to yourself. Of course, if they are not the same sexuality as you this could make matters harder for you but that doesn't mean you can't be open with them about it, you just won't be guaranteed being with them.