Normal weight gain???

My doctor gave me a hard time about weight gain, she said that I shouldn't have gained any weight in the first 2 trimesters - I'm 5'9" weighing 140 pre pregnancy and have gained 12 pounds at 21 weeks. Everything I have read makes this seem normal to me, but now I'm feeling uncomfortable eating. How much weight have you ladies been gaining? I'm really upset - she was very unprofessional referring to me "packing on the pounds" - this seems ridiculous, I'm pregnant!