OMD! That would have pissed me off, too. And if I'd had that nurse in my class, she would have undergone a long lecture on why that was a totally inappropriate thing to say.
It must be so difficult (well, impossible) not to worry but I'm so glad to know you are taking steps to deal with it - and glad you have a doctor who has learnt to respect your opinions on your own condition, even if he has to double check. Yoga sounds like a great idea - hope it has speedy positive effects.