Your attachment to this guy you call your best friend is unhealthy. I wonder if he, in some way, is encouraging you to hang on to him. He shouldn't. You are infatuated with him to the point of obsession. That is not any basis for true friendship. You are pouring a ton of psychic energy into a direction that is going nowhere.

Find a female friend, or even just a female associate. Feel free to flirt with men you're attracted to, but not after you've been solidly rejected. You're losing out on opportunities because your attention is focused on going down a dead end path.

Therapy might benefit you. Your pattern of behavior is deeply entrenched and would be hard to change. But change is needed. You see how this approach to life is getting you nowhere. With help, you might be able to break out of this. You deserve more than constant unrequited attachment. Life could offer you more, but you must first let go of futile behavior.