I think most people who feel the need to pick on others are either ignorant about the disorder or have some personal insecurity. You can't control them but you can control your reaction. They want to make you feel bad. I think in cases like these, as annoying as it is, you should take the high road and ignore them. You know that you are not worthless. That's the important thing. Who cares what they say?

If its really bullying, I would tell a teacher and let them deal with it.