I have been prescribed medications I was told by other doctors not totake, and told "it'll be fine". The doctor relied on the fact that it was late in the day and I was tired, not likely to wage a long battle with him. I objected as strenuously as I had energy for, and he kept repeating "it'll be fine"; it was obvious that nothing was going to get him to change his mind. (Though maybe I should've "gotten dramatic", called upon my trained soprano skills and started screaming at a volume that would get other medical staff to come running.)
Two days later, another doctor asked "are they trying to kill you?" and told me that if I wanted to try that medication, I should only do it in a hospital or nursing home where they could react immediately to any medical emergency that might result; my offer to have a nurse-friend stay the weekend with me was not good enough: she would not have the necessary equipment at hand when something went terribly wrong (as was highly likely). I'd had dramatic side effects from a related medication, and NEVER should have been given any other medication in that family. I knew that, the pharmacist knew that, but the prescribing doctor either didn't know or didn't care (or, as the second doctor mused, was trying to kill me because my claim against the medical group for malpractice would die along with me).
Thank God I'd been educated the first time around not to ever again take anything in that family, and didn't blindly trust the doctor's assertion "it'll be fine". In that case, getting in the doctor's face was not enough. I had to be pro-active and not fill the prescription, and talk to another doctor about it. Theoretically, alerting the pharmacist to my prior reaction would have gotten him on the phone to the doctor for a different prescription, with more effect than my own request for something else. But, obviously, after hearing from the second doctor that they were trying to kill me, I chose not to trust anything else they might prescribe and walked away from that medical group.
Working with a doctor to regain your health should not be an adversarial procedure, but for too many CFS patients it becomes exactly that: poorly-informed doctors want to treat you for depression, not for viral and neurological problems, and wind up making you sicker, perhaps permanently.
You need to take charge of your own medical care, and not trust the doctors to get it right. They're human, they make mistakes. Don't be afraid to question them. The life you save may be your own.