Told a friend at school who then blackmailed me to tell everyone else in our friend group or she'd tell the whole school.

I'm so sorry you had to go through that :( your experience is actually quite similar to mine. I realised a little later than you (13/14) when I also started to develop sexual feelings. The first friend I told reacted very badly, and barely talked to me from that moment on and suddenly lots of people already knew about me and used to bully me or constantly ask me if I liked girls or if I didn't like men or dick in a derogotaroty tone :( until I left that school, 4 years later, basically LOTS of people who didn't even know me, knew that I was lesbian. I lost friends... Oh well, I'm glad it's over!