Do I have a case for constructive discharge?

I have been working at a medical office for 6 years as an administrative assistant and my employer recently told me that I would have to start working in the clinical part of the office. I do not have any type of nursing, medical assistant, LPN, etc., degree to do this type of work. Some of my new duties include taking x-rays, finishing medical procedures, dressing wounds, etc. After 4 weeks of training for this new position, I went to my employer and told him that I was not qualified or comfortable in my new position. I was basically repremanded by my employer and told that I could not have my old job back. I feel that my only choices are to continue this work or quit. I don't even know if I can legally do this type of work without having been medically trained. I am very uncomfortable treating patients without any kind of certification. What are my options?