Most doctors don't like to keep patients on opioids long term if it can possibly be avoided. He may just be trying to find a combination of non-opioid medications that will still relieve your pain.
Don't hesitate to ask him why he wants to switch your medications and express your concerns to him. As long as you're not confrontational, he should be willing to explain his reasoning to you. It's important that you and your doctor work together as a team to manage your pain. If your doctor won't talk with your or work with you, it's probably time to find another doctor.
Good luck to you.