Most definitely talk to the doctor...even if it means getting an "emergency" appointment. My doctor keeps time available if someone needs to come in unexpectedly. It is an emergency because you can't function and work on a few hours of sleep a night.
I bet he doesn't know he has such a mouthy medical assistant. She has no right to talk to you that way and then basically threaten you. If he did drop you as a patient, I'd report him. He took the Hippocratic Oath and he needs to live up to it. But, honestly, I just bet he doesn't know she is throwing her weight around with his patients. Who knows...she might be the one out there looking...looking for another job!
Sherrine