First of all, I am very sorry to hear you are in so much pain. It can be very difficult indeed.
Be as honest with your doctor as possible. It is more likely that if you are honest with your history, and describe that you understand he may be reluctant to prescribe pain medication to a new patient, you are however, in a great deal of pain. He may very well prescribe some vicodin or percocet but not give you a large quantity. Make sure you keep all appointments and be open to physical therapy or other modalities he may suggest.
There are other muscle relaxers other than flexeral also, that you may respond to. Keep an open mind. He may want to try you on one of those.
After seeing your primary care doctor for a while, if he is not getting good results with controlling your pain, know that he may refer you to a pain specialist or pain clinic. They specialize in chronic pain and often help people who are like yourself and can't get adequate relief.
But definitely try this new doctor this appointment, be honest and cooperative and place your cards on the table. Be respectful and develop a relationship with your doctor. Chances are you will be successful in your quest to overcome your pain and suffering from your condition.
Hope this has helped.