So I like of my best friends but I never intended to tell her because she hated people liking her but she suddenly changed her mind & started dating a guy I don’t like & now I can’t think of anything but her… what now?

You  talk to your mom. It’s the best place to start, in my pinion. Take it from there. Regardless, I think professional therapy should happen. Good for you for halting the action, even if temporarily. Just maybe, then, it can be permanent. I wish you the best of luck.