Unfortunatelly, I have... But I have learned that you should NEVER back down!
As in this very well made video, many young people get's bullied everyday. And some of these beautifull humanbeing get's bullied to suicide.
I can just say, don't ever back down on what they say about you! You are just as perfect, if not even more perfect than the bullies! Normally bullies actually feel like they have to bully others just so they won't get bullied themselves. They can easilly have problems themselves, that they just wanna forget about. So they are trying to make others feel bad, to help themselves feel better...
I know many adult tell you the exact same thing, but actually it often is true.
The best way to stop being bullied is to make the bully know they are not gonna gain anything from it. If you don't show them it's hurtfull, and act like you don't care. They mostly don't think it's funny anymore.
I have tried that, and it actually really did work.
There were these boy's from another class on my school, whom always threw stuff at me, and tried to block my way... I just ignored them. And threw anything they have thrown at me back to them, without saing a word, and just walked away.
Actually some day, in the morning they were trying to block my way, while they were standing on each side of the small hallway, with their feet together, like a barrier or something. They just stood there, looked at me and laughed.
And I just looked at them, then looked at their legs. And took a big step over the legs, and walked away. While I walked away one of them yelled: "Come on it's not funny if you don't care!"
So there you go... And that was just the one time I tried it. Just keep cool, act like you don't care, and walk the way you want to. They have no right telling you, that you are nothing, cuz you know what? You are more than them!