Haha yeah. I'm blonde too =]
Are the people that call you "blonde" brunette by any chance? They're probably just jealous hun...and anyway, why is being blonde an insult?! It doesn't make you stupid at all...I'm in the top group at school and about half our class is naturally blonde.
As for the "toothpick" thing, I'd say it's jealousy again. If you're 13, my guess is that your friends bodies are changing and yours maybe isn't developing, or maybe just not as first? Some girls can be very insecure about their curves when they first get them, so they make fun of skinny girls to make them feel better.
The truth is that the world is full of women who would absolutely love to be skinny and blonde. Learn to love it - and NEVER dye your hair brown or try to gain weight!!!!