If you write an affidavit of non-compliance with your CPAP and your medical doctor will not write a prescription for an oral appliance then you are stuck.
If your medical doctor will not help you out then you can seek out another medical doctor who is willing to work with your CPAP intolerance.
Another option is to have you start the sleep apnea screening process over with Dr. Nugent and his board certified sleep doctors who are current with oral appliance therapy protocols. Our office can help you get around your Medical Doctor lack of cooperation. We have set up a work flow that partners with Board Certified Sleep Physicians that understand the important role dentists play in making mandibular advancement devices when appropriate.