Thanks, ya'll. I was a little afraid I was overreacting. I think I will call and talk to the dr in the morning. I talked to my grandmother (who has been an RN for over 30 years) and she said what that nurse said was both unethical and unprofessional and she should absolutely be reported. Then she told me I should use what she said as incentive to lose weight.
I've always been tiny too. I'm barely 5'4" and my weight has always stayed between 95 and 100 pounds. I've put on a good 70 pounds since last June.