Fighting won't do anything unless you happen to be an absolute fighting machine. And even then everything you’re going to do will probably just get you into trouble, espically because whoever is bullying you will become really angry and very likely just get a couple of friends to fire back at you.
Telling a teacher or an adult will at best solve the problem for a few days.
After that it will start all over again.
Trust me I tried it and it does absolutely nothing.
There is exactly one thing that you can do.
And its to not let the things that people say about you get to you, especially if its about your appearance. If you constantly treat things like that as a personal attack and get anygry because of it, people aren't gonna stop. Instead they are going to notice that you're getting angry and continue to provoke you because...well it’s kind of sad but seeing people angry from an outside view is just hilarious. I mean why do you think rage compilations on youtube exist?
What you should be trying to do instead is to treat it with humor, even if it seems difficult. And I don't mean just laughing it off with a little grin, you can actually play into it, even make jokes about yourself.
That way you can show people that you absolutely don’t care about any of your flaws or even make any insults regarding you look a little ridiculous in the first place no matter if the intention behind it was serious or not.
All in all thats probably gonna make you seem a lot more charismatic and confident than trying to fight them.
