can i be forced to give up doctor/patient confidentiality by the doctor?

You cannot be "forced" to give up the doctor-patient confidentiality privlege. However, if your doctor were brought into a legal or administrative proceeding, it is possible that information about your treatment with this doctor could be requested. The doctor is probably concerned because of the length of time, quantity or both, of opiate medication you have been taking, and his becoming liable for misprescribing it. The doctor cannot verify you are not selling it, so this sounds like a precautionary measure.

The bigger question to me would be: what will you do if legal authorities contact you about your use of vicodin? Even if you have done nothing wrong, I suggest that you contact a criminal attorney before you answer any questions. If you talk about your medical history with them, it is possible you will waive the confidentiality privilege.

A doctor could stop prescribing medication to you but it would have to be based on valid medical information/history about the patient. You also can choose a different doctor or at least obtain a consultation with a pain management specialist about other options you may have for for managing your back pain. Have you considered going to a pain management clinic or seeing someone who specialises in pain management? Do you really want to keep taking opiates if you have other non narcotic options for managing your pain? There are a lot of possible options out there for back pain management that do not require use of narcotic drugs. I strongly suggest that you explore these options with either this doctor or with another back specialist or pain management doctor.